U.S. patent application number 12/443065 was filed with the patent office on 2010-11-11 for organic-inorganic hybrid chiral sorbent and process for the preparation thereof.
This patent application is currently assigned to COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH. Invention is credited to Syed Hasan Razi Abdi, Santosh Agarwal, Raksh Vir Jasra, Noor-ul Hasan Khan, Rukhsana Ilyas Kureshy, Vishal Jitendrabhai Mayani.
Application Number | 20100286425 12/443065 |
Document ID | / |
Family ID | 40590081 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100286425 |
Kind Code |
A1 |
Abdi; Syed Hasan Razi ; et
al. |
November 11, 2010 |
ORGANIC-INORGANIC HYBRID CHIRAL SORBENT AND PROCESS FOR THE
PREPARATION THEREOF
Abstract
The present invention provides an organic-inorganic hybrid
chiral sorbent for chiral resolution of various racemic compounds
viz. racemic mandelic acid, 2-phenyl propionic acid, diethyl
tartrate, 2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and cyano
chromene oxide with excellent chiral separation (enantiomeric
excess, 99%) in case of mandelic acid under medium pressure column
chromatography. These optically pure enantiomers find applications
as intermediates in pharmaceutical industries.
Inventors: |
Abdi; Syed Hasan Razi;
(Bhavnagar, IN) ; Kureshy; Rukhsana Ilyas;
(Bhavnagar, IN) ; Khan; Noor-ul Hasan; (Bhavnagar,
IN) ; Jasra; Raksh Vir; (Bhavnagar, IN) ;
Mayani; Vishal Jitendrabhai; (Bhavnagar, IN) ;
Agarwal; Santosh; (Bhavnagar, IN) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
1290 Avenue of the Americas
NEW YORK
NY
10104-3800
US
|
Assignee: |
COUNCIL OF SCIENTIFIC &
INDUSTRIAL RESEARCH
New Delhi
IN
|
Family ID: |
40590081 |
Appl. No.: |
12/443065 |
Filed: |
August 30, 2007 |
PCT Filed: |
August 30, 2007 |
PCT NO: |
PCT/IN2007/000376 |
371 Date: |
July 12, 2010 |
Current U.S.
Class: |
556/410 |
Current CPC
Class: |
B01J 20/103 20130101;
B01J 20/29 20130101; B01J 20/3092 20130101; B01J 2220/58 20130101;
B01J 2220/54 20130101; B01J 20/3217 20130101; C07B 57/00 20130101;
B01J 20/28083 20130101; B01J 20/3204 20130101; B01J 20/3261
20130101; B01J 20/3257 20130101; B01J 20/3259 20130101; B01J
20/3263 20130101; B01J 20/286 20130101 |
Class at
Publication: |
556/410 |
International
Class: |
C07F 7/18 20060101
C07F007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2006 |
IN |
2160/DEL/2006 |
Claims
1. An organic-inorganic hybrid chiral sorbent comprising amino
alcohol covalently bonded to the surface of mesoporous silica
material.
2. A product according to claim 1, wherein the amino alcohol used
is amino propyl alcohol.
3. A product according to claim 1, wherein the porous silica
material used is having porosity in the range of 37 to 100 .ANG.
and is selected from the group consisting of MCM-41, SBA-15 and
MCF-48.
4. A product according to claim 1, wherein the product obtained is
represented by the group of following chiral sorbents:
(S)-aminopropyl alcohol@silica-41, (R)-aminopropyl
alcohol@silica-41, (S)-aminopropyl alcohol@silica-15,
(R)-aminopropyl alcohol@silica-15, (S)-aminopropyl
alcohol@silica-F, (R)-aminopropyl alcohol@silica-F, (S)--N-methyl
aminopropyl alcohol@silica-41, (R)--N-methyl aminopropyl
alcohol@silica-41, (S)--N,N'dimethyl aminopropyl alcohol@silica-41,
(S)--N,N'dimethyl aminopropyl alcohol@silica-15 and (S)--N-methyl
aminopropyl alcohol@silica-15
5. A product according to claim 1, wherein the chiral sorbent is
useful for the separation of racemic mixture of compound selected
from the group consisting of mandelic acid, 2-phenyl propionic
acid, diethyl tartrate, 2,2'-dihydroxy-1,1'-binaphthalene (BINOL)
and cyano chromene oxide.
6. A process for the preparation of an organic-inorganic hybrid
chiral sorbent, the said process comprising the steps of: a)
silylating the chiral epoxide with a silylating agent in an organic
solvent with a molar ratio of chiral epoxide to silylating agent of
about 1:1 in the presence of an inorganic base in the range of 1:1
to 1:2.5, b) refluxing, the above said reaction mixture obtained in
step (a) under an inert atmosphere for a period of 8 to 16 hours,
followed by filtration to obtain the resultant filtrate, c)
refluxing, the above said filterate obtained in step (b) with
mesoporous silica, under inert atmosphere for a period of about 35
to 55 hours, followed by filtration and washing of the resultant
solid product with toluene by known methods, d) reacting the
resultant washed product obtained in step (c) with aniline or
substituted aniline in toluene, under reflux, under an inert
atmosphere for a period of 8 to 16 hours, followed by filtration
and washing off the resultant product with toluene and extracting
the desired chiral sorbent in a solution mixture of toluene and
isopropanol by known methods to obtain the desired product of
organic-inorganic hybrid chiral sorbent.
7. A process according to claim 6, wherein the chiral epoxide used
in step(a) is selected from the group consisting of propene oxide,
1-chloro-2,3-epoxypropane, 1-fluoro-2,3-epoxypropane,
1-bromo-2,3-epoxypropane, 1-methyl-2,3-epoxypropane,
1-methoxy-2,3-epoxypropane and 1-nitro-2,3-epoxypropane.
8. A process according to claim 6, wherein the silylating agent
used in step(a) is selected from the group consisting of
chloropropyl triethoxysilane, chloropropyltrimethoxy,
nitropropyltriethoxysilane, aminopropyltriethoxysilane and
aminopropyltrimethoxysilane.
9. A process according to claim 6, wherein the inorganic base used
in step (a) is selected from the group consisting of sodium
carbonate, potassium carbonate, rubidium carbonate and cesium
carbonate.
10. A process according to claim 6, wherein the organic solvent
used in step(a) is selected from the group consisting of ethanol,
methanol, isopropanol, acetone, acetonitrile, toluene,
tetrahydrofuran, dichloroethane and dichloromethane.
11. A process according to claim 6, wherein the mesoporous silica
used in step (c) is selected from the group consisting of MCM-41,
SBA-15 and MCF-48.
12. A process according to claim 6, wherein the inert atmosphere
used is provided by using inert gas selected from nitrogen, argon
and helium.
13. A process according to claim 6, wherein the molar amount of
aniline or substituted aniline with respect to chiral epoxide is in
the range of 1:1 to 1:2.
14. A process according to claim 6, wherein the substituted aniline
used is selected from the group consisting of nitroaniline,
chloroaniline, methoxyaniline and methylaniline.
15. A process according to claim 6, wherein the amount of
mesoporous silica used is in the range of 0.8 to 12 g/mmol of
chiral epoxide.
16. A process according to claim 6, wherein the chiral sorbent
obtained in step(d) is represented by the group of following
sorbents: mandelic acid, 2-phenyl propionic acid, diethyl tartrate,
2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and cyano chromene
oxide.
17. A process according to claim 6, wherein the chiral sorbent
obtained is useful for the separation of racemic mixtures of
compound selected from the group consisting of mandelic acid,
2-phenyl propionic acid, diethyl tartrate,
2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and cyano chromene
oxide.
18. A process according to claim 17, wherein the enantiomeric
excess of racemates obtained is in the range of 30 to 99%.
19. A process according to claim 18, wherein the maximum
enantiomeric excess obtained for mandelic acid with
aminopropylalcohol@silica sorbent is about 99%.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an organic-inorganic hybrid
chiral sorbent. More particularly it relates to optically pure
covalently bonded amino alcohol to mesoporous silica as chiral
selector for chiral resolution of various racemic compounds, viz.
racemic mandelic acid, 2-phenyl propionic acid, diethyl tartrate,
2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and cyano chromene oxide
under medium pressure column chromatography. The present invention
further relates to a process for the preparation of
organic-inorganic hybrid chiral sorbent. These optically pure
enantiomers find applications as intermediates in pharmaceutical
industries.
BACKGROUND OF THE INVENTION
[0002] Resolution of chiral molecules is required in many areas of
research. As enzymes and other biological receptor molecules are
stereo-specific, enantiomers of a racemic compound may interact
with them in a different manner. Consequently, two enantiomers of a
racemic compound have different pharmacological activities in many
instances. In order to discern these differing effects, the
biological activity of each enantiomer needs to be studied
separately.
[0003] This has contributed significantly towards the requirement
of enantiomerically pure compounds particularly in pharmaceutical
industry and thereby the needs to focus on chiral separation using
techniques like chiral chromatography. Various attempts have been
made in the past for the development of different stationary
phases; for example A. Bielejewska et al. Chem. Anal. (Warsaw) 47
(2002) 419 has reported .beta.-cyclodextrin (p-CD) and
permethylated .beta.-cyclodextrin for use of chromatographic
separation of mandelic acid and its esters of different aliphatic
carbon chain length by reverse phase HPLC. The drawbacks of this
process are; (i) .beta.-cyclodextrin alone does not recognize
enantiomers of mandelic acid; (ii) stationary phase needs to be
permethylated for achieving high chiral separation; (iii) reaction
has to be conducted in reverse phase.
[0004] S. P. Mendez et al. J. Anal. At. Spectrom. 13 (1998) 893.
reported the resolution of D,L-selenomethionine derivatives of OPA
(O-phthalaldehyde) and NDA (2,3-naphthalenedicarboxaldehyde) to
their respective enantiomers by HPLC on a .beta.-CD chiral column
using conventional fluorimetric detection. The drawbacks of this
process are; (i) In this study, the amino acid was derivatized
using o-phthalaldehyde or naphthalene-2,3-dicarboxaldehyde to allow
conventional fluorimetric detection. Such a derivatization step,
however, is undesirable because it prolongs the sample preparation
time, and requires additional validation because it may be a
potential source of contamination, may induce racemization or may
complicate the separation.
[0005] L. S. Karen et al. Analyst 125 (2000) 281 disclosed the work
based on a commercially available HPLC column with a chiral crown
ether based stationary phase to perform enantiomeric separations of
selenoamino acids without derivatization. The drawbacks of this
process are; (i) the need to have dilute perchloric acid as mobile
phase for such a column; (ii) The separation of the enantiomers is
temperature sensitive.
[0006] C. A. L. Ponce de Leon et al. J. Anal. At. Spectrom. 15
(2000) 1103 describes the enantiomeric separation of nine
selenoamino acids encountered in selenium-enriched yeast using a
crown ether column. The drawbacks of this process are; (i) this
reaction involves acidic condition to get effective separation;
(ii) The separation process requires lower temperature
(18-22.degree. C.) for complete resolution; (iii) the non-polar
amino acids may not elute from the column, therefore, a balance
between temperature and elution of non-polar compounds is required
for an optimum separation.
[0007] S. P. Mendez et al. J. Anal. At. Spectrom. 15 (2000) 1109
described the use of teicoplanin-bonded chiral stationary phase
(Chirobiotic T) to resolve a variety of underivatized aminoacids.
Teicoplanin is a glycopeptide antibiotic which contains 20 chiral
centers. The drawbacks of this process are; (i) Teicoplanin is a
toxic and naturally occurring complex molecule therefore cannot be
easily tuned for various applications (ii) due to the presence of
many glycosidic linkages it is prone to hydrolysis and/or
alteration in conformation thereby change in optical properties
under the elution conditions (iii) this separation process requires
pH adjustment about 4 and 7; (iv) separation has to be conducted in
reverse phase.
[0008] M. Raimondo et al. Chem. Commun. (1997) 1343 used mesoporous
silica-based MCM-41 coated on GC capillary columns, as chiral
stationary phase to separate different organic molecules The
drawbacks of this process are; (i) That separation indeed occurs
within the MCM-41 cavities and by a mechanism depending on the
proton affinities of the compounds.
[0009] M. Grun et al. J. Chromatogr. A 740 (1996) 1 described the
behavior of silica, alumina, titania, zirconia and the novel
mesoporous aluminosilicate MCM-41 in normal-phase high-performance
liquid chromatography under comparable conditions. MCM-41 shows
some interesting features as compared to mesoporous crystalline and
amorphous oxides. The drawbacks of this process are; (i) This work
includes only comparison of an ordered mesoporous aluminosilicate,
silica, alumina, titania and zirconia in normal-phase
high-performance liquid chromatography; (ii) it requires very large
column (250.times.4 mm).
[0010] V. A. Soloshonok, Angew. Chem., Int. Ed. 45 (2006) 766),
reported the work based on achiral silica as column packing
material for remarkable separation of enantiomers of perfluoroalkyl
keto compounds through column chromatography. The drawbacks of this
process are; (i) only trifluoromethyl group containing compounds
are separated. (ii) variation in results is found with changing the
solvents. (iii) In the case of preferential homochiral association,
the situation is bit subtle as the formation of dimer will result
in different number of enantiomeric (S)(S) and (R)(R) pairs with
identical scalar properties. These dimers therefore cannot be
separated.
[0011] J. H. Kennedy, J. Chromatogr. A 725 (1996) 219 disclosed
chiral stationary phases based on polysaccharide derivative coated
on silica for chiral separation of different compounds containing
carbonyl group and other aromatic ring containing compounds. The
drawbacks of this process are; (i) Derivatization of carboxylic
acids or eluent modifiers such as acetic acid or diethyl amine is
required in this system;.(ii) Polysaccharide phases based chiral
stationary phase is not predictable and capable of separating both
t-acid and n-basic type compounds.
[0012] X. Huang et al. Analytical Science 21 (2005) 253 and S.
Rogozhin et al. German Patent 1 932 190 (1969); Chem. Abstr., 72
(1970) 90875c have described the use of chiral copper metal complex
supported on silica as stationary phase for separation
DL-selenomethionine in buffered solution at pH, 5.5 along with
methanol as mobile phase. The drawbacks of this process is (i) This
separation technique requires 200.times.4.6 mm i.d. stainless-steel
column; (ii) only underivatized amino acids were resolved on it;
(iii) the use of methanol doesn't favor the resolution of
DL-selenomethionine; (iv) higher temperature gives some
de-activation effect of some biological sample.
[0013] J. Bergmann et al. Anal. Bioanal. Chem. 378 (2004) 1624 and
M. M. Bayon et al. J. Anal. At. Spectrom. 16(9) (2001) 945
disclosed a fast and sensitive method for the determination of the
absolute configuration of Se-amino acids by derivatization process
at room temperature by reversed-phase high-performance liquid
chromatography-inductively coupled plasma-mass spectrometry. The
drawbacks of these process are; (i) separation can be possible in
reversed phase HPLC-inductively coupled plasma-mass spectrometry;
(ii) Detection limits of about 4 microg L(-1) were obtained; (iii)
The derivetization of enantiomers of selenomethionine is necessary.
(iv) The final operating conditions involved the use of 50% (v/v)
MeOH at pH 5.3 (acetic acid--sodium acetate).
[0014] H. Kosugi et al. Chem. Commun. (1997) 1857 described
synthesis of (-)-epibatidine and its intermediates by medium
pressure liquid chromatography by using achiral silica gel column
(Si-10; eluted with 3:1 hexane-EtOAc; UV (254 nm) and RI
detectors). The drawbacks of this process are; (i) In this system
there is no mechanism of the separation: (ii) It includes only
synthesis of (-)-epibatidine and its intermediates; (iii) only
hydroxy acetal was separated through achiral column
chromatography.
[0015] S. P. Mendez et al. J. Anal. At. Spectrom. 14 (1999) 1333
described chiral resolution and speciation of DL-selenomethionine
enantiomers by capillary gas chromatography (GC) using an
L-valine-tert-butylamide modified polydimethylsiloxane as chiral
stationary phase The drawbacks of this process are; (i) good
resolution was achieved in the higher temperature range only from
100-160.degree. C.; (ii) requires He as carrier gas; (iii)
separation is more difficult for complex biological samples.
[0016] R. Vespalec et al. Anal. Chem. 67 (1995) 3223; K. L. Sutton
et al. Analyst 125 (2000) 231; S. P. Mendez et al. Anal. Chim. Acta
416 (2000) 1; J. A. Day et al. J. Anal. At. Spectrom. 17 (2002) 27
describes capillary electrophoresis as a tool for the enantiomeric
separation selenium containing amino acids, by derivatization
process using capillary electrophoresis with UV absorbance
detection. The drawbacks of this process are; (i) This separation
technique has been used to separate the enantiomers of selenoamino
acids by the addition of chiral additives to the electrophoretic
buffer; (ii) UV absorbance detection was used in these studies and
required the derivatization of the selenoamino acids to permit
detection; (iii) UV absorbance detection, without sample
pre-concentration, was not sensitive enough to permit the detection
of the low levels of selenoamino acids present in complex samples;
(iv) applied voltage and pH value gives variation in separation
results; (v) buffer system was chosen for good resolution; (vi)
addition of methanol to the buffer is required for improved
resolution.
[0017] B. V. Ernholt et al. Eur. J. Chem. 6 (2000) 278) described
the synthesis and enzymatic separation of 1-Azafagomine through
achiral regular column chromatography. The drawbacks of this
process are; (i) enzymetic separation requires different buffer
solutions; (ii) the conversion and enantiomeric excess is affected
by varying the solvents, enzymes and its concentration; (iii) low
enantiomeric excess was achieved through achiral column
chromatography by loading 51% compound.
[0018] A. Goswami et al., Z Tetrahedron Asymmetry, 16 (2005) 1715
disclosed enzymatic separation of (.+-.)-sec-butlylamine, lipase
and proteases using ether, heptane or dacane as solvent and vinyl
butyrate or ethyl, butyrate as acylating agent. The drawbacks of
this process are; (i) enzymes shows very low enantio-selectivity;
(ii) it's a time consuming process (more than 7 days); (iii)
solvent, such as acetonitrile, cyclohexane, toluene, methyl-t-butyl
ether, 2-methyl-2-pentanol, ethyl caprate is required for this
system. Mitsuhashi Kazuya et at in U.S. Pat. No. 278,268 Oct. 23,
2002 disclosed a method for the synthesis of optically active
mandelic acid derivatives by enzymatic separation. The drawbacks of
this process are; (i) microorganism is essential to generate the
(R)-mandelic acid derivative or (S)-mandelic acid derivative; (ii)
requires appropriate buffer solution.
[0019] Mori Takao et al. U.S. Pat. No. 142,914 Oct. 29, 1993
disclosed a process for preparing D-mandelic acid by converting
L-mandelic acid into benzoylformic acid followed by
stereoselectively reducing it into D-mandelic acid. The drawbacks
of this process are; (i) The isolation and collection of microbial
cells from culture broth is complicated; (ii) buffer solution is
required for maintaining pH; (iii) it is time consuming
process.
[0020] Endo Takakazu et at in U.S. Pat. No. 677,175 Mar. 29, 1991
disclosed process for producing (R)-(-)-mandelic acid or a
derivative through enzymatic separation. The drawbacks of this
process are; (i) hydrolysis of mandelonitrile is necessary; (ii)
requires neutral or basic reaction system to produce the
(R)-(-)-mandelic acid; (iii) requires expensive use of
microorganism and Ghisalba Oreste et at in U.S. Pat. No. 360,802
Jun. 2, 1989 described process for the preparation of R- or
S-2-hydroxy-4-phenylbutyric acid in very high enantiomeric purity
by enzymatic separation. Disadvantage of this process are; (i) The
reduction of the substrate is effected by the so-called final
reductase; (ii) suitable as biocatalysts are only purified enzymes;
(iii) regeneration of enzyme is complicated.
[0021] Hashimoto Yoshihiro et at in U.S. Pat. No. 764,295 Dec. 12,
1996, reported a process for producing an alpha-hydroxy acid or an
alpha-hydroxyamide from an aldehyde and prussic acid with a
microorganism. The drawbacks of this process are; (i) deactivation
of microorganism within a short period of time at higher and lower
temperature; (ii) high concentration and high yield is difficult to
obtain for alpha-hydroxy acid or alpha-hydroxyamide; (iii) the
reaction rate is lowered with an increase in the concentration of
the alpha-hydroxy acid or alpha-hydroxyamide product as a result,
the reaction does not proceed to completion.
[0022] Endo Takakazu et al in U.S. Pat. No. 904,335 Jun. 25, 1992
described a process for producing (R),(S)-mandelic acid or a
derivative thereof from mandelonitrile using a microorganism
belonging to the genus Rhodococcus. The drawbacks of this process
are; (i) chiral reagents and microorganism are more expensive; (ii)
this method is industrially non-advantageous for producing
(R)-(-)-mandelic acid or derivatives; (iii) hydrogenases produced
by these bacteria are not always satisfactory.
[0023] R. Charles et al. J. Chromatogr. 298 (1984) 516 described
the separation of .sup.14C labelled nicotine through totally
achiral column chromatography. The drawbacks of this process are;
(i) it requires buffer solution to adjust the pH; (ii)
peak-splitting phenomenon was caused by some components of the
cation-exchange column or mobile phase.
[0024] V. A. Soloshonok et al. J. Fluorine Chemistry, In Press
disclosed the self-disproportionation chromatography (SDC) involves
the separation of trifluoromethyl group containing compounds and
used totally achiral silica as column packing. The drawbacks of
this process are; (i) variations in results are found with changing
the solvents. (ii) In the case of preferential homochiral
association, the situation is bit subtle as the formation of dimmer
will result in different number of enantiomeric (S)(S) and (R)(R)
pairs with identical scalar properties. These dimers therefore
cannot be separated.
OBJECTIVES OF THE INVENTION
[0025] The main object of the present invention is to provide an
organic-inorganic hybrid chiral sorbent
[0026] Another object of the invention is to provide a process for
the preparation of organic-Inorganic hybrid chiral sorbent.
[0027] Yet another object of the present invention is to provide a
process for chiral resolution of racemic compounds using optically
pure amino alcohols covalently attached on mesoporous silica as
chiral selector for chiral resolution of various racemic compounds
viz. racemic mandelic acid, 2-phenyl propionic acid, diethyl
tartrate, 2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and cyano
chromene.
[0028] Yet another object of the present invention is to provide
chiral resolution of racemic compounds using optically pure amino
alcohol covalently attached on mesoporous silica as chiral selector
for achieving high Enantiomeric Excess (ee) (99%) at room
temperature.
[0029] Yet another object of the present invention is to provide
chiral resolution of racemic compounds using optically pure amino
alcohol covalently attached on mesoporous silica as chiral selector
under medium pressure slurry system.
[0030] Still another object of the present invention is to provide
chiral resolution of racemic compounds using optically pure amino
alcohol covalently attached on mesoporous silica as chiral selector
under medium pressure (0.5 kp/cm.sup.2) column chromatography.
SUMMARY OF THE INVENTION
[0031] Accordingly, the present invention provides an
organic-inorganic hybrid chiral sorbent comprising amino alcohol
covalently bonded to the surface of mesoporous silica material.
[0032] In an embodiment of the present invention the amino alcohol
used is amino propyl alcohol.
[0033] In another embodiment of the present invention the porous
silica material used is having porosity in the range of 37 to 100
.ANG. and is selected from the group consisting of MCM-41, SBA-15
and MCF-48.
[0034] In yet another embodiment the product obtained in the
present invention is represented by the group of following chiral
sorbent selected from (S)-aminopropyl alcohol@silica-41,
(R)-aminopropyl alcohol@silica-41, (S)-aminopropyl
alcohol@silica-15, (R)-aminopropyl alcohol@silica-15,
(S)-aminopropyl alcohol@silica-F, (R)-aminopropyl alcohol@silica-F,
(S)--N-methyl aminopropyl alcohol@silica-41, (R)--N-methyl
aminopropyl alcohol@silica-41, (S)--N,N'dimethyl aminopropyl
alcohol@silica-41, (S)--N,N'dimethyl aminopropyl alcohol@silica-15
and (S)--N-methyl aminopropyl alcohol@silica-15
[0035] In yet another embodiment of the invention the chiral
sorbent is useful for the separation of racemic mixture of
compounds selected from the group consisting of mandelic acid,
2-phenyl propionic acid, diethyl tartrate,
2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and cyano chromene
oxide.
The present invention further provides a process for the
preparation of an organic-inorganic hybrid chiral sorbent, the said
process comprising the steps of: [0036] a) silylating the chiral
epoxide with a silylating agent in an organic solvent with a molar
ratio of chiral epoxide to silylating agent in the range of 1:1 to
1:2.5, in the presence of an inorganic base, [0037] b) refluxing,
the above said mixture obtained in step (a) under an inert
atmosphere for a period of 8 to 16 hours, followed by filtration to
obtain the resultant filterate, [0038] c) refluxing, the above said
filterate obtained in step (b) with mesoporous silica, under inert
atmosphere for a period of about 35 to 55 hours, followed by
filtration and washing of the resultant solid product with toluene
by known methods, [0039] d) reacting the resultant washed product
obtained in step (c) with aniline or substituted aniline in
toluene, under reflux, under an inert atmosphere for a period of 8
to 16 hours, followed by filtration and washing off the resultant
product with toluene and extracting the desired chiral sorbent in a
solution mixture of toluene and isopropanol by known methods to
obtain the desired product of organic-inorganic hybrid chiral
sorbent.
[0040] In yet another embodiment the chiral epoxide used in step(a)
is selected from the group consisting of propene oxide,
1-chloro-2,3-epoxypropane, 1-fluoro-2,3-epoxypropane,
1-bromo-2,3-epoxypropane, 1-methyl-2,3-epoxypropane,
1-methoxy-2,3-epoxypropane and 1-nitro-2,3-epoxypropane.
[0041] In yet another embodiment the silylating agent used in
step(a) is selected from the group consisting of chloropropyl
triethoxysilane, chloropropyltrimethoxy,
nitropropyltriethoxysilane, aminopropyltriethoxysilane and
aminopropyltrimethoxy silane.
[0042] In yet another embodiment the inorganic base used in step
(a) is selected from the group consisting of sodium carbonate,
potassium carbonate, rubidium carbonate and cesium carbonate.
[0043] In yet another embodiment the organic solvent used in
step(a) is selected from the group consisting of ethanol, methanol,
isopropanol, acetone, acetonitrile, toluene, tetrahydrofuran,
dichloroethane and dichloromethane.
[0044] In yet another embodiment the mesoporous silica used in step
(c) is selected from the group consisting of MCM-41, SBA-15 and
MCF-48.
[0045] In yet another embodiment the inert atmosphere used is
provided by using inert gas selected from nitrogen, argon and
helium.
[0046] In yet another embodiment the molar amount of aniline or
substituted aniline with respect to chiral epoxide is in the range
of 1:1 to 1:2.
[0047] In yet another embodiment the substituted aniline used is
selected from the group consisting of nitroaniline, chloroaniline,
methoxyaniline and methylaniline.
[0048] In yet another embodiment the amount of mesoporous silica
used is in the range of 0.8 to 12 g/mmol of chiral epoxide.
[0049] In yet another embodiment the chiral sorbent obtained in
step(d) is represented by the group of following sorbents: mandelic
acid, 2-phenyl propionic acid, diethyl tartrate,
2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and cyano chromene
oxide.
[0050] In yet another embodiment the chiral sorbent obtained is
useful for the separation of racemic mixtures of compound selected
from the group consisting of mandelic acid, 2-phenyl propionic
acid, diethyl tartrate, 2,2'-dihydroxy-1,1'-binaphthalene (BINOL)
and cyano chromene oxide.
[0051] In yet another embodiment the enantiomeric excess of
racemates obtained is in the range of 30 to 99%.
[0052] In still another embodiment the maximum enantiomeric excess
obtained for mandelic acid with aminopropylalcohol@silica sorbent
is about 99%.
DESCRIPTION OF THE INVENTION
[0053] According to the present invention describes the preparation
of organic-inorganic hybrid chiral sorbent, which comprises of
[0054] i) silylation of chiral epoxide in the concentration range
of 2.557 to 25.57 mmol with aminopropyl
triethoxysilane/N-methylaminopropyl triethoxysilane in the
concentration range of 2.55 to 25.57 mmol in the presence of
K.sub.2CO.sub.3/Na.sub.2CO.sub.3 in the concentration range of 5.1
to 51 mmol in dry tetrahydrofuran; [0055] ii) refluxing the
reaction mixture in the step i) under N.sub.2Ar/He atmosphere in
the time range of 8 to16 h; [0056] iii) filtrating the reaction
mixture of step ii) to obtain clear solution; [0057] iv) refluxing
the clear solution of step (iii) with mesoporous silica in the
range of 2 g to 20 g in dry toluene under N.sub.2/Ar/He atmosphere
for a period of 35 to 55 h; [0058] v) filtration of reaction
mixture of step iv) to obtain solid material, followed by washing
with toluene and Soxhlet extraction in toluene; [0059] vi) reacting
the washed material obtained in step (v) with aniline/substituted
anilines in the concentration range of 5 to 50 mmol under reflux
condition in N.sub.2/Ar/He atmosphere for a period of 8-16 h in
toluene; [0060] vii) filtration of solid sorbent in step vi)
followed by washing with toluene, Soxhlet extraction in
toluene/isopropanol in the range (9:1 to 7:3) and dried in vacuum;
[0061] viii) Taking the chiral column packing material from step
vii) in the concentration range of 0.128 to 0.512 mol % [0062] ix)
Making slurry of chiral packing material to step viii) by using
hexane/isopropanol as column packing solvents in the ratio of
(9.5:0.5) to (8:2) and packing in a 260.times.16 mm glass column;
[0063] x) loading of analyte on the packed column from step ix) as
solid or dissolving in hexane/isopropanol ratio (1:1) in the
concentration range 0.50 to 3.00 mol %; [0064] xi) elution of
solvents through column in step x) using hexane/isopropanol in the
ratio of (9.5:0.5) to (8:2) using medium-pressure (0.25-0.75
kp/cm.sup.2) of nitrogen/argon/helium at room temperature; [0065]
xii) collecting the chromatographic fractions (1-12), (13-24) and
(25-36) from step xi) in the range of 2 to 6 ml per fraction with
an increment of 2 ml after 12 fractions; [0066] xiii) maintaining
the medium-pressure (0.25-0.75 kp/cm.sup.2) of
nitrogen/argon/helium at room temperature through out the step xii)
[0067] xiv) examining each collected fractions from step xi to
xiii) on an appropriate chiral HPLC column.
[0068] The synthesis process of amino alcohol modified silica was
conducted on laboratory scale in a 100 ml three-necked round bottom
flask fitted with an efficient water condenser using
S-(+)-epichlorohydrin, 3-aminopropyl triethoxysilane, aniline and
silica. The medium pressure column chromatography was carried out
by making slurry of (S)-amino alcohol@silica 1 in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The analyte solution in isopropanol/hexane (1:1) was
loaded on thus packed column that was equilibrated for 1 h. The
elution of fractions was done at the pressure mentioned above. Each
fraction was subjected to HPLC analysis using an appropriate chiral
column. Different analytical grade compounds were used as an
analytes. The absolute configuration of different compound was
determined by the comparison of HPLC profile with authentic
samples.
[0069] The separation process according to the present invention
was carried out by using amount of analyte in the range of 10 to 30
mg, preferably using 2 g amino alcohol immobilized on silica as
column packing material at medium-pressure (0.5 kp/cm.sup.2) of
nitrogen at room temperature. Higher separation of mandelic acid
was obtained when the amount of analyte was more than 10 mg. The
chiral products were characterized by the comparison of HPLC
profile with authentic samples. In the preferred embodiment, the
pressure of the column is maintained (0.25-0.75 kp/cm.sup.2) of
nitrogen at room temperature. In accordance with the present
invention, the chiral amino alcohol immobilized on silica plays a
very vital role in achieving better separation of analytes. The
amino alcohol used to separate analyte is 2 g. With low quantity of
amino alcohol modified silica the separation is sluggish. The use
of optimal quantity amino alcohol modified silica (2 g) is
essential as it definitely separates the different analyte.
[0070] In carrying out the present invention, the time required for
the chromatographic separation of analytes is more than 7 h to
achieve higher enantiomeric excess. The time of separation may be
varied by increasing pressure, it was observed that decreasing the
time of chromatographic separation below 5 h resulted in lower
separation of analyte
[0071] The present invention relates to the preparation of chiral
compounds suitable for various applications. These chiral compounds
were separated from racemic compounds by medium pressure
chromatographic separation using amino alcohol as selector at
medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room temperature.
The chromatographic separation of racemic compounds was found to be
higher than that reported in literature where the separation
depends on i) derivatization of stationary phase as well as
analyte, ii) pH of eluents iii) high temperature requirement that
result into diffusional problems, reproducibility and difficulty in
their reuse. The method of present invention does not require any
special device.
The inventive steps adopted in the present invention are:-- [0072]
(i) generating chirality on inorganic silica surface by covalently
binding the simple and readily available chiral organic compounds
through silanol groups present on the silica surface. [0073] (ii)
Using surface bound chiral amino alcohol as a selector for the
chromatographic separation of different compounds at room
temperature. [0074] (iii) the resolution of racemic compound is
carried out at medium-pressure (0.5 kp/cm.sup.2) of nitrogen;
[0075] In a typical chromatographic resolution run, the appropriate
amino alcohol as selector, hexane/isopropanol as eluents was packed
into 260.times.16 mm glass column using medium-pressure slurry
system (0.5 kp/cm.sup.2) at room temperature. The analyte solution
in isopropanol/hexane (1:1) was loaded on thus packed column that
was equilibrated for 1 h. Each fraction was subjected to HPLC
analysis using an appropriate chiral column.
[0076] The following examples are given by way of illustration of
the present invention and therefore should not be construed to
limit the scope of the present invention.
Example-1
[0077] Step 1:
(2'S)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-triethoxysilane
[0078] (S)-(-)-epichlorohydrine (0.2 ml), 3-aminopropyl triethoxy
silane (0.598 g), potassium carbonate (0.705 g) and dry
tetrahydrofuran were charged in a 3-necked 50 ml round bottom flask
equipped with a mechanical stirrer, addition funnel and a reflux
condenser connected to a nitrogen inlet. The resulting mixture was
stirred at room temperature for 10 minutes and followed by
refluxing the mixture for 12 h. The reaction mixture was filtered
under an inert atmosphere. Solvent from the filtrate was removed by
the dry nitrogen draft
[0079] Yield; (0.674 g, 95%).
[0080] Step 2:
(S)-amino propyl epoxy@silica-41
[0081] The product of step 1 (0.674) was dissolved in dry toluene
in a 3-necked 50 ml round bottom flask in an inert atmosphere. The
dissolved mass was treated with MCM-41 (2.0 g) for 48 h. at the
refluxing temperature of toluene. The reaction mass was filtered
and washed with dry toluene for several time then dried under
vacuum. The dried material was subjected to Soxhlet extraction with
dry toluene for 10 h followed by drying the sample under vacuum.
Yield; (2 g, loading 22.5% by TGA)
[0082] Step 3:
(S)-aminopropyl alcohol@silica-41
[0083] The epoxy product from the step 2 (22.5% loading, 2 g) was
treated with aniline (455 .mu.l) in 10 ml dry toluene in an inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with dry toluene and subjected to Soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. C. Yield; (2 g, loading
25.6% by TGA).
Example-2
[0084] Step 1:
(2'R)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-triethoxysilane
[0085] (R)-(-)-epichlorohydrine (0.2 ml), 3-aminopropyl triethoxy
silane (0.598 g), potassium carbonate (0.705 g) and dry
tetrahydrofuran were reacted and processed in the manner it was
done in step 1 of the example 1. Yield (0.680 g, 96%).
[0086] Step 2:
(R)-aminopropyl epoxy@silica-41
[0087] The product of step 1 (0.674) was dissolved in dry toluene
in 3-necked 50 ml round bottom flash in an inert atmosphere. Then
this dissolved mass was treated with MCM-41 (2.0 g) for 48 h at
refluxing temperature. The reaction mixture was processed as per
the method given in step 2 of the example 1. (2 g, loading 22.0% by
TGA)
[0088] Step 3:
(R)-aminopropyl alcohol@silica-41
[0089] The epoxy product from the step 2 (22.0% loading, 2 g) was
treated with aniline (455 .mu.l) in 10 ml dry toluene in inert
atmosphere. The suspension was treated as per the method given in
step 3 of the example 1. Yield (2 g, loading 25.0% by TGA).
Example-3
[0090] Step 1:
(2'S)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-trimethoxysilane
[0091] (S)-(-)-epibromohydrine (0.2 ml), 3-aminopropyl trimethoxy
silane (0.598 g), potassium carbonate (0.705 g) and dry diethyl
ether were charged in a 3-necked 50 ml round bottom flask equipped
with a mechanical stirrer, addition funnel and a reflux condenser
connected to a nitrogen inlet. The resulting mixture was stirred at
room temperature for 10 minutes and followed by refluxing the
mixture for 10 h. The reaction mixture was filtered under inert
atmosphere. Solvent from the filtrate was removed by the dry
nitrogen draft. Yield (0.65 g, 95%).
[0092] Step 2:
(S)-aminopropyl epoxy@silica-15
[0093] The product of step 1 (0.65 g) was dissolved in dry toluene
in 3-necked 50 ml round bottom flask in an inert atmosphere. Then
this dissolved mass was treated with SBA-15 (2.0 g) for 48 h. at
refluxing temperature. The reaction mass was filtered and washed
with dry toluene for several time then dried under vacuum. The
dried material was subjected to Soxhlet extraction with dry toluene
for 10 h followed by drying the sample under vacuum. (2.2 g,
loading 24.0% by TGA)
[0094] Step 3:
(S)-aminopropyl alcohol@silica-15
[0095] The epoxy product from the step 2 (24.0% loading, 2 g) was
treated with aniline (500 .mu.l) in 10 ml dry toluene in an inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with dry toluene and subjected to the soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. c. (2 g, loading
26.5%).
Example-4
[0096] Step 1:
(2'R)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-tributoxysilane
[0097] (R)-(-)-epichlorohydrine (0.2 ml), 3-aminopropyl
tributoxysilane (0.598 g), Sodium carbonate (0.700 g) and dry
tetrahydrofuran were charged in a 3-necked 50 ml round bottom flask
equipped with a mechanical stirrer, addition funnel and a reflux
condenser connected to a nitrogen inlet. The resulting mixture was
stirred at room temperature for 10 minutes and followed by
refluxing the mixture for 12 h. The reaction mixture was filtered
under inert atmosphere. Solvent from the filtrate was removed by
the dry nitrogen draft: yield (0.60 g, 94%).
[0098] Step 2:
(R)-aminopropyl epoxy@silica-15
[0099] The product of step 1 (0.674) was dissolved in dry toluene
in 3-necked 50 ml round bottom flash in inert atmosphere. Then this
dissolved mass was treated with SBA-15 (2.0 g) for 48 h. at
refluxing temperature. Reaction was further processed as per the
step 2 of the example 3. (2 g, loading 26.0% by TGA).
[0100] Step 3:
(R)-aminopropyl alcohol@silica-15
[0101] The epoxy product from the step 2 (26.0% loading, 2 g) was
treated with aniline (500 .mu.l) in 10 ml dry toluene in inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with dry toluene and subjected to the soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. C. (2 g, loading
26.2%).
Example-5
[0102] Step 1:
(2'S)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-trimethoxysilane
[0103] Synthesized as per the method given in step 1 of the example
1.
[0104] Step 2:
(S)-aminopropyl epoxy@silica-F
[0105] The product of step 1 (0.674 g) was dissolved in dry toluene
in 3-necked 50 ml round bottom flask in an inert atmosphere. Then
this dissolved mass was treated with MCF (2.0 g) for 48 h. at
refluxing temperature. The reaction mass was filtered and washed
with dry toluene for several time then dried under vacuum. The
dried material was subjected to Soxhlet extraction with dry toluene
for 10 h followed by drying the sample under vacuum.(2.2 g, loading
27.0% by TGA)
[0106] Step 3:
(S)-aminopropyl alcohol@silica-F
[0107] The epoxy product from the step 2 (27.0% loading, 2 g) was
treated with aniline (600 .mu.l) in 10 ml dry toluene in inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with dry toluene and subjected to the soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. C. (2 g, loading
27.6%).
Example-6
[0108] Step 1:
(2'R)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-trimethoxysilane
[0109] This material was synthesized as per the method described in
step 1 of the example 1.
[0110] Step 2:
(R)-aminopropyl epoxy@silica-F
[0111] The product of step 1 (0.674 g) was dissolved in dry toluene
in 3-necked 50 ml round bottom flash in inert atmosphere. Then this
dissolved mass was treated with MCF (2.0 g) and processed as per
the method of step 2 of example 5. Yield; 2 g, loading 26.5% by
TGA.
[0112] Step 3:
(R)-aminopropyl alcohol@silica-F
[0113] The epoxy product from the step 2 (26.5% loading, 2 g) was
treated with aniline (600 .mu.l) in 10 ml dry toluene in an inert
atmosphere and the reaction was processed as per the step 3 of the
example 5. (Yield; 2 g, loading 27.0%).
Example-7
[0114] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0115] (S)-(-)-epichlorohydrine (0.2 ml), 3-N-methylaminopropyl
trimethoxy silane (0.700 g), potassium carbonate (0.705 g) and dry
toluene were charged in a 3-necked 50 ml round bottom flask
equipped with a mechanical stirrer, addition funnel and a reflux
condenser connected to a nitrogen inlet. The resulting mixture was
stirred at RT for 10 minutes and followed by refluxing the mixture
for 16 h. The reaction mixture was filtered under inert atmosphere.
Solvent from the filtrate was removed by the dry nitrogen draft:
yield (0.715 g, 96%).
[0116] Step 2:
(S)--N-methyl aminopropyl epoxy@silica-41
[0117] The product of step 1 (0.700 g) was dissolved in dry toluene
in 3-necked 50 ml round bottom flask in an inert atmosphere. The
reaction mixture was treated with MCM-41 (2 g) for 48 h. at the
refluxing temperature of toluene. The reaction mass was filtered
and washed with dry toluene for several time then dried under
vacuum. The dried material was subjected to Soxhlet extraction with
dry toluene for 10 h followed by drying the sample under vacuum
(2.2 g, loading 20.5% by TGA)
[0118] Step 3:
(S)--N-methyl aminopropyl alcohol@silica-41
[0119] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with aniline (455 .mu.l) in 10 ml dry toluene in an inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with dry toluene and subjected to the soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. C. (2 g, loading
25.6%).
Example-8
[0120] Step 1:
(2'R)--N'-(2',3'-epoxypropyl)-3-(N-methylaminoaminopropyl)-trimethoxysilan-
e
[0121] (R)-(-)-epichlorohydrine (0.2 ml), 3-N-methylaminopropyl
trimethoxy silane (0.598 g), sodium carbonate (0.705 g) and dry
methanol were charged in a 3-necked 50 ml round bottom flask
equipped with a mechanical stirrer, addition funnel and a reflux
condenser connected to a nitrogen inlet. The reaction was processed
as per the method given in step 1 of the example 7. Yield (0.725 g,
97%).
[0122] Step 2:
(R)--N-methyl aminopropyl epoxy@silica-41
[0123] The product of step 1 (0.700 g) was dissolved in dry toluene
in 3-necked 50 ml round bottom flask in inert atmosphere. Then this
dissolved mass was treated with MCM-41 (2.0 g) in the manner
described in step 2 of the example 7. (2.0 g, loading 21.0% by
TGA)
[0124] Step 3:
(R)--N-methyl aminopropyl alcohol@silica-41
[0125] The epoxy product from the step 2 (21.1% loading, 2 g) was
treated with aniline (455 .mu.l) in 10 ml dry toluene in an inert
atmosphere. The reaction was processed as per the method described
in step 3 of the example 7. Yield (2 g, loading 25.0%).
Example-9
[0126] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0127] This material was synthesized by following the method given
in step 1 of the example 7.
[0128] Step 2:
(S)--N-methyl aminopropyl epoxy@silica-15
[0129] The product of step 1 (0.674 g) was dissolved in dry toluene
in 3-necked 50 ml round bottom flask in an inert atmosphere. Then
this dissolved mass was treated with SBA-15 (2.0 g) for 48 h. at
refluxing temperature. The reaction mass was filtered and washed
with dry toluene for several time then dried under vacuum. The
dried material was subjected to Soxhlet extraction with dry toluene
for 10 h followed by drying the sample under vacuum. Yield (2.4 g,
loading 23.5% by TGA).
[0130] Step 3:
(S)--N-methyl aminopropyl alcohol@silica-15
[0131] The epoxy product from the step 2 (23.5% loading, 2 g) was
treated with aniline (600 .mu.l) in 10 ml dry toluene in an inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with dry toluene and subjected to the soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. C. (2 g, loading
26.8%).
Example-10
[0132] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0133] This material was prepared by the method described in the
step 1 of the example 7.
[0134] Step 2:
(S)--N-methyl aminopropyl epoxy@silica-41
[0135] this material was prepared by following the procedure given
in step 2 of the example 7.
[0136] Step 3:
(S)--N,N' dimethyl aminopropyl alcohol@silica-41
[0137] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with N-methylaniline (600 .mu.l) in 10 ml dry toluene in an
inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-11
[0138] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0139] This material was prepared by the method described in the
step 1 of the example 7.
[0140] Step 2:
(S)--N-methyl aminopropyl epoxy@silica-41
[0141] This material was prepared by following the procedure given
in step 2 of the example 7.
[0142] Step 3:
(S)--N-methyl aminopropyl alcohol@silica-41
[0143] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-methyl aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhiet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-12
[0144] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0145] This material was prepared by the method described in the
step 1 of the example 7.
[0146] Step 2:
(S)--N-methyl aminopropyl epoxy@silica-41
[0147] This material was prepared by following the procedure given
in step 2 of the example 7.
[0148] Step 3:
(S)--N-methyl aminopropyl alcohol@silica-41
[0149] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-chloro aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-13
[0150] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0151] This material was prepared by the method described in the
step 1 of the example 7.
[0152] Step 2:
(S)--N-methyl aminopropyl epoxy@silica
[0153] This material was prepared by following the procedure given
in step 2 of the example 7.
[0154] Step 3:
(S)--N-methyl aminopropyl alcohol@silica-41
[0155] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-methoxy aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-14
[0156] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0157] This material was prepared by the method described in the
step 1 of the example 5.
[0158] Step 2:
(S)-aminopropyl epoxy@silica-F
[0159] this material was prepared by following the procedure given
in step 2 of the example 5.
[0160] Step 3:
(S)-aminopropyl alcohol@silica-F
[0161] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-methoxy aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-15
[0162] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0163] This material was prepared by the method described in the
step 1 of the example 5.
[0164] Step 2:
(S)-aminopropyl epoxy@silica-F
[0165] this material was prepared by following the procedure given
in step 2 of the example 5.
[0166] Step 3:
(S)-aminopropyl alcohol@silica-F
[0167] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-chloro aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-16
[0168] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0169] This material was prepared by the method described in the
step 1 of the example 5.
[0170] Step 2:
(S)-aminopropyl epoxy@silica-F
[0171] this material was prepared by following the procedure given
in step 2 of the example 5.
[0172] Step 3:
(S)-aminopropyl alcohol@silica-F
[0173] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-methyl aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-17
Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0174] This material was prepared by the method described in the
step 1 of the example 9.
[0175] Step 2:
(S)--N-methylaminopropyl epoxy@silica-15
[0176] This material was prepared by following the procedure given
in step 2 of the example 9.
[0177] Step 3:
(S)--N,N'-dimethyl aminopropyl alcohol@silica-15
[0178] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-methyl aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-18
[0179] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0180] This material was prepared by the method described in the
step 1 of the example 9.
[0181] Step 2:
(S)--N-methyl aminopropyl epoxy@silica-15
[0182] This material was prepared by following the procedure given
in step 2 of the example 9.
[0183] Step 3:
(S)--N-methyl aminopropyl alcohol@silica-15
[0184] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-methoxy aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-19
[0185] Step 1:
(2'S)--N'-(2',3'-epoxypropyl)-3-(N-methylaminopropyl)-trimethoxysilane
[0186] This material was prepared by the method described in the
step 1 of the example 9.
[0187] Step 2:
(S)--N-methylaminopropyl epoxy@silica-15
[0188] This material was prepared by following the procedure given
in step 2 of the example 9.
[0189] Step 3:
(S)--N-methyl aminopropyl alcohol@silica-15
[0190] The epoxy product from the step 2 (20.5% loading, 2 g) was
treated with 4-chloro aniline (600 .mu.l) in 10 ml dry toluene in
an inert atmosphere. The suspension was refluxed for 18 h. The
reaction mixture was cooled to room temperature and the solid was
filtered, washed repeatedly with dry toluene and subjected to the
soxhlet extraction with toluene and isopropanol (7:3) for 10 h.
Finally the sample was dried under vacuum at 40.degree. C. (2 g,
loading 23.5%).
Example-20
[0191] Step 1:
(2'S)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-triethoxysilane
[0192] (S)-(-)-Ephedrine (0.2 ml), 3-aminopropyl triethoxy silane
(0.598 g), potassium carbonate (0.705 g) and dry tetrahydrofuran
were charged in a 3-necked 50 ml round bottom flask equipped with a
mechanical stirrer, addition funnel and a reflux condenser
connected to a nitrogen inlet. The resulting mixture was stirred at
RT for 10 minutes and followed by refluxing the mixture for 12 h.
The reaction mixture was filtered under an inert atmosphere.
Solvent from the filtrate was removed by the dry nitrogen draft:
Yield; (0.674 g, 95%).
[0193] Step 2:
(S)-aminopropyl epoxy@silica-41
[0194] The product of step 1 (0.674) was dissolved in dry toluene
in a 3-necked 50 ml round bottom flask in an inert atmosphere. The
dissolved mass was treated with MCM-41 (2.0 g) for 48 h. at the
refluxing temperature of toluene. The reaction mass was filtered
and washed with dry toluene for several time then dried under
vacuum. The dried material was subjected to Soxhlet extraction with
dry toluene for 10 h followed by drying the sample under vacuum.
Yield; (2 g, loading 22.5% by TGA)
[0195] Step 3:
(S)-aminopropyl alcohol@silica-41
[0196] The epoxy product from the step 2 (22.5% loading, 2 g) was
treated with aniline (455 .mu.l) in 10 ml dry toluene in an inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with dry toluene and subjected to Soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. c. Yield; (2 g, loading
25.6% by TGA).
Example-21
[0197] Step 1:
(2'S)--N-(2',3'-epoxypropyl)-3-(aminopropyl)-triethoxysilane
[0198] (S)-(-)-PsaudoEphedrine (0.2 ml), 3-chloro propyl triethoxy
silane (0.598 g), potassium carbonate (0.705 g) and dry
tetrahydrofuran were charged in a 3-necked 50 ml round bottom flask
equipped with a mechanical stirrer, addition funnel and a reflux
condenser connected to a nitrogen inlet. The resulting mixture was
stirred at RT for 10 minutes and followed by refluxing the mixture
for 12 h. The reaction mixture was filtered under an inert
atmosphere. Solvent from the filtrate was removed by the dry
nitrogen draft: Yield; (0.674 g, 95%).
[0199] Step 2:
(S)-aminopropyl epoxy@silica-41
[0200] The product of step 1 (0.674) was dissolved in dry toluene
in a 3-necked 50 ml round bottom flask in an inert atmosphere. The
dissolved mass was treated with MCM-41 (2.0 g) for 48 h. at the
refluxing temperature of toluene. The reaction mass was filtered
and washed with dry toluene for several time then dried under
vacuum. The dried material was subjected to Soxhlet extraction with
dry toluene for 10 h followed by drying the sample under vacuum.
Yield; (2 g, loading 22.5% by TGA)
[0201] Step 3:
(S)-aminopropyl alcohol@silica-41
[0202] The epoxy product from the step 2 (22.5% loading, 2 g) was
treated with aniline (455 .mu.l) in 10 ml dry toluene in an inert
atmosphere. The suspension was refluxed for 12 h. The reaction
mixture was cooled to room temperature and the solid was filtered,
washed repeatedly with -dry toluene and subjected to Soxhlet
extraction with toluene and isopropanol (7:3) for 10 h. Finally the
sample was dried under vacuum at 40.degree. C. Yield; (2 g, loading
25.6% by TGA).
Example-22
[0203] In a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.128 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The solid racemic mandelic acid (3.00 mol %) was
loaded on packed column that was equilibrated for 1 h. The elution
of fractions was done at the pressure mentioned above. Each
fraction was subjected to HPLC analysis using an appropriate
Chiralcel OD column, eluent hexane/isopropanol (9:1) at 220 nm. The
enantiomeric excess of mandelic acid found 7.4%.
Example-23
[0204] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.128 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The solid racemic mandelic acid (3.00 mol %) was
loaded on packed column that was equilibrated for 1 h. The elution
of fractions was done at the pressure mentioned above. Each
fraction was subjected to HPLC analysis using an appropriate
Chiralcel OD column, eluent hexane/isopropanol (9:1) at 220 nm. The
enantiomeric excess, enantiomeric excess of mandelic acid found
7.4%.
Example-24
[0205] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.512 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The solid racemic mandelic acid (1.50 mol %) was
loaded on packed column that was equilibrated for 1 h. The elution
of fractions was done at the pressure mentioned above. Each
fraction was subjected to HPLC analysis using an appropriate
Chiralcel OD column, eluent hexane/isopropanol (9:1) at 220 nm. The
enantiomeric excess of mandelic acid found 8.3%.
Example-25
[0206] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.512 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The racemic mandelic acid (1.50 mol %) dissolved in
isopropanol/hexane (1:1) was loaded on packed column that was
equilibrated for 1 h. The elution of fractions was done at the
pressure mentioned above. Each fraction was subjected to HPLC
analysis using an appropriate Chiralcel OD column, eluent
hexane/isopropanol (9:1) at 220 nm. The enantiomeric excess of
mandelic acid found 99.4%.
Example-26
[0207] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.486 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The racemic mandelic acid (1.58 mol %) dissolved in
isopropanol/hexane (1:1) was loaded on packed column that was
equilibrated for 1 h. The elution of fractions was done at the
pressure mentioned above. Each fraction was subjected to HPLC
analysis using an appropriate Chiralcel OD column, eluent
hexane/isopropanol (9:1) at 220 nm. The enantiomeric excess of
mandelic acid found 99.0%.
Example-27
[0208] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.479 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The racemic mandelic acid (1.60 mol %) dissolved in
isopropanol/hexane (1:1) was loaded on packed column that was
equilibrated for 1 h. The elution of fractions was done at the
pressure mentioned above. Each fraction was subjected to HPLC
analysis using an appropriate Chiralcel OD column, eluent
hexane/isopropanol (9:1) at 220 nm. The enantiomeric excess of
mandelic acid found 98.8%.
Example-28
[0209] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.512 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The racemic mandelic acid (0.50 mol %) dissolved in
isopropanol/hexane (1:1) was loaded on packed column that was
equilibrated for 1 h. The elution of fractions was done at the
pressure mentioned above. Each fraction was subjected to HPLC
analysis using an appropriate Chiralcel OD column, eluent
hexane/isopropanol (9:1) at 220 nm. The enantiomeric excess,
enantiomeric excess of mandelic acid found 98.5%
Example-29
[0210] To a medium pressure chromatographic column, slurry of
MCM-41 (0.512 mol %) in hexane and isopropanol (9:1) was packed in
a 260.times.16 mm glass column using medium-pressure (0.5
kp/cm.sup.2) of nitrogen at room temperature. The racemic mandelic
acid (0.50 mol %) dissolved in isopropanol/hexane (1:1) was loaded
on thus packed column that was equilibrated for 1 h. The elution of
fractions was done at the pressure mentioned above. Each fraction
was subjected to HPLC analysis using an appropriate Chiralcel OD
column, eluent hexane/isopropanol (9:1) at 220 nm. No separation of
mandelic acid was found.
Example-30
[0211] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.512 mol %) in hexane and
isopropanol (8:2) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The racemic 2,2'-dihydroxy-1,1'-binaphthalene (BINOL)
(0.50 mol %) dissolved in isopropanol/hexane (1:1) was loaded on
packed column that was equilibrated for 1 h. The elution of
fractions was done at the pressure mentioned above. Each fraction
was subjected to HPLC analysis using an appropriate Chiralpak AD
column, eluent hexane/isopropanol (8:2) at 254 nm. The enantiomeric
excess, enantiomeric excess of 2,2'-dihydroxy-1,1'-binaphthalene
(BINOL) found 19.5%.
Example-31
[0212] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.512 mol %) in hexane and
isopropanol (9:1) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The racemic cyanochromene oxide (CNCR) (0.50 mol %)
dissolved in isopropanol/hexane (1:1) was loaded on packed column
that was equilibrated for 1 h. The elution of fractions was done at
the pressure mentioned above. Each fraction was subjected to HPLC
analysis using an appropriate Chiralcel OD column, eluent
hexane/isopropanol (9:1) at 254 nm. The enantiomeric excess
cyanochromene oxide (CNCR) of found 3.8%.
Example-32
[0213] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.512 mol %) in hexane and
isopropanol (8:2) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The solution of racemic diethyl-tartrate (0.50 mol %)
in isopropanol/hexane (1:1) was loaded on packed column that was
equilibrated for 1 h. The elution of fractions was done at the
pressure mentioned above. Each fraction was subjected to HPLC
analysis using an appropriate Chiralpak AD column, eluent
hexane/isopropanol (8:2) at 220nm. The enantiomeric excess of
diethyl-tartrate found 11.5%.
Example-33
[0214] To a medium pressure chromatographic column, slurry of
(S)-aminopropyl alcohol@silica 1 (0.512 mol %) in hexane and
isopropanol (9.5:0.5) was packed in a 260.times.16 mm glass column
using medium-pressure (0.5 kp/cm.sup.2) of nitrogen at room
temperature. The solution of racemic 2-phenyl propionic acid (0.50
mol %) in isopropanol/hexane (1:1) was loaded on thus packed column
that was equilibrated for 1 h. The elution of fractions was done at
the pressure mentioned above. Each fraction was subjected to HPLC
analysis using an appropriate Chiralcel OD column, eluent
hexane/isopropanol/formic acid (9:8.1) at 254nm. The enantiomeric
excess of 2-phenyl propionic acid found 33.5%
Example-34
[0215] The same procedure as exemplified in example 1 was repeated
with various racemic compounds viz., 2-phenyl propionic acid,
diethyl tartrate, 2,2'-dihydroxy-1,1'-binaphthalene (BINOL) and
cyano chromene oxide under medium pressure column chromatography.
The results are summarized in Table 1 and 2.
TABLE-US-00001 TABLE 1 Separation of Mandelic acid varying amount
of Mandelic acid and packing material Amount of Column Loading
Mandelic Packing of acid Material.sup.c Mandelic Absolute Entry
m.mol 1(g) acid.sup.e (%) Eluent.sup.f % ee max.sup.g configuration
1 0.099.sup.a 0.50 3.0 Hex/IPA = 9:1 7.4 R 2 0.197.sup.a 2.00 1.5
Hex/IPA = 9:1 8.3 R 3 0.197.sup.b 2.00 1.5 Hex/IPA = 9:1 99.4 R 4
0.197.sup.b 1.90 1.5 Hex/IPA = 9:1 99.0 R 5 0.197.sup.b 1.87 1.5
Hex/IPA = 9:1 98.8 R 6 0.066.sup.b 2.00 0.5 Hex/IPA = 9:1 98.5 R 7
0.066.sup.b MCM-41.sup.d 0.5 Hex/IPA = 9:1 -- R + S (50:50%)
.sup.aMandelic acid loaded on column as solid, .sup.bMandelic acid
loaded on column after dissolving in Isopropanol/Hexane,
.sup.c(S)-amino propyl alcohol@silica is used as column packing
material .sup.dMCM-41 is used as column packing material (2 gm),
.sup.epercentage loading of mandelic acid according to column
packing material, .sup.fHex = hexane, IPA = isopropanol,
.sup.gEnantiomeric Excess of R-mandelic acid using HPLC chiralcel
OD column, eluent Hexane/IPA = 9:1 at 220 nm., .sup.habsolute
configuration were determined by the comparison of HPLC profile
with authentic samples.
TABLE-US-00002 TABLE 2 Data for separation of different compounds
by flash column chromatography.sup.a Column Name of Sample Packing
compound amount.sup.f Material % ee Absolute Entry (racemic) (mg) 1
(g) Eluent.sup.g max configuration.sup.h 8 BINOL.sup.b 10 2.0
Hex/IPA = 8:2 19.5 R 9 CNCR.sup.c 10 2.0 Hex/IPA = 9:1 3.8 3S,4S 10
Diethyl 10 2.0 Hex/IPA = 8:2 11.5 2R,3R Tartrate.sup.d 11 2-phenyl
10 2.0 Hex/IPA = 9.5:0.5 33.5 S Propionic acid.sup.e .sup.aAll the
experiments were conducted under the same condition unless
otherwise stated. Temperature (27.degree. C.), amount of sample m =
0.0100 .+-. 0.0001 g, column diameter d = 16 mm, length = 260 mm,
Enantiomeric excess was determined by HPLC analysis by mentioned
columns. (l = 25 cm, d = 0.46 cm). .sup.bChiralpak AD column,
eluent Hexane/IPA = 8:2 at 254 nm. .sup.cCyanochromene oxide(CNCR)
chiralcel OD column, eluent Hexane/IPA = 9:1 at 254 nm.
.sup.dChiralpak AD column, eluent Hexane/IPA = 9:1 at 220 nm.
.sup.eChiralcel OD column, eluent Hexane/IPA/Formic acid = 98:2:1
at 254 nm. .sup.fAnalyte loaded on column after dissolving in
Isopropanol/Hexane. .sup.gHex = hexane, IPA = isopropanol.
.sup.hThe absolute configuration were determined by the comparison
of HPLC profile with authentic samples.
ADVANTAGES OF THE INVENTION
[0216] Resolution of different compounds is achievable with
inexpensive medium pressure column chromatography. [0217] Organic
selector based amino alcohol modified silica (2 g) is sufficient
enough for the separation of enantiomers in the present invention
at room temperature. [0218] Only smaller quantity of column packing
material is required to carry out for the repeated experiments
using medium pressure column chromatography. [0219] Organic
solvents like hexane and isopropanol are used as column packing
solvents as well as eluents. [0220] Under the defined
chromatographic conditions the resolution of enantiomers is carried
out by medium-pressure range from (0.25-0.75 kp/cm.sup.2) of
nitrogen at room temperature. [0221] Separation chromatography is
carried out in air and no prior oxygen free conditions are
required. [0222] A simple glass column is required for packing
purpose. [0223] Using the present invention high resolution of
racemates having excellent enantiomeric excess was achieved within
reasonable time period that makes the process viable for industrial
application. [0224] By carrying out the Soxhlet extraction process,
the amino alcohol modified silica can be reused for repeated
experiments.
* * * * *