U.S. patent application number 11/178661 was filed with the patent office on 2005-12-01 for kinase mimic catalysts for asymmetric synthesis of phosphorylated inositols and cycloalkanols.
This patent application is currently assigned to The Trustees of Boston College. Invention is credited to Miller, Scott J., Morgan, Adam J., Sculimbrene, Bianca.
Application Number | 20050267291 11/178661 |
Document ID | / |
Family ID | 23168539 |
Filed Date | 2005-12-01 |
United States Patent
Application |
20050267291 |
Kind Code |
A1 |
Miller, Scott J. ; et
al. |
December 1, 2005 |
Kinase mimic catalysts for asymmetric synthesis of phosphorylated
inositols and cycloalkanols
Abstract
The present invention provides peptide-based phosphorylation
catalysts (PBPC's) for the asymmetric monophosphorylation of
cyclitols, particularly myo-inositols. The PBPC's of the invention
effect a regio and enantioselective phosphorylation of a
myo-inositol in a manner analogous to enzymatic kinases, thereby
functioning as effective "kinase mimics." Although orders of
magnitude less complex in terms of structure than macromolecular
proteins, the PBPC's of the invention control product formation
with high enantioselectivity (>98% ee). The synthetic
(+)-myo-inositol-1-phosphate is optically and spectroscopically
equivalent to naturally occurring compound. The ability of the low
molecular weight PBPC's of the present invention to mimic
stereoselective enzymes represents a powerful approach toward
catalytic asymmetric synthesis of biologically important molecules,
and for mechanistic modeling of biochemical transformations to
enable their use in drug applications.
Inventors: |
Miller, Scott J.; (Needham,
MA) ; Sculimbrene, Bianca; (Newton, MA) ;
Morgan, Adam J.; (North Scituate, RI) |
Correspondence
Address: |
PALMER & DODGE, LLP
PAULA CAMPBELL EVANS
111 HUNTINGTON AVENUE
BOSTON
MA
02199
US
|
Assignee: |
The Trustees of Boston
College
|
Family ID: |
23168539 |
Appl. No.: |
11/178661 |
Filed: |
July 11, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11178661 |
Jul 11, 2005 |
|
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|
10187208 |
Jul 1, 2002 |
|
|
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60302621 |
Jul 2, 2001 |
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Current U.S.
Class: |
530/329 ;
530/330; 530/331; 548/335.5 |
Current CPC
Class: |
C07K 7/06 20130101; C07K
7/02 20130101 |
Class at
Publication: |
530/329 ;
530/330; 530/331; 548/335.5 |
International
Class: |
C07K 005/06; C07K
007/06; C07K 005/04 |
Goverment Interests
[0002] The present invention was made with support in part from the
National Institute of Health Grant No. GM-57595 and the National
Science Foundation Grant No. CHE-9874963. The United States
Government retains certain rights to the invention.
Claims
What is claimed is:
1. A compound of the formula 13wherein R.sub.1 is a lower alkyl;
R.sub.2 is an amine protecting group; and Pep is a peptide
comprising a peptide residue including at least one natural or
non-natural amino acid and having at least one phosphorous
moiety.
2. The compound of claim 1 wherein R.sub.1.dbd.C.sub.1 to C.sub.6
straight or branched chain alkyl, R.sub.2 is a carbamate, and Pep
is a monopeptide, an oligopeptide or a polypeptide comprising at
least one amino acid.
3. The compound of claim 2 wherein the carbamate is selected from
the group consisting of t-butyl carbamate, 9-fluorenylmethyl
carbamate, benzyl carbamate and ortho-nitrobenzyl carbamate.
4. The compound of claim 1 wherein R.sub.1 is CH.sub.3 and R.sub.2
is t-butylcarbamate.
5. The compound of claim 1 wherein Pep is a an oligopeptide or a
polypeptide comprising a sequence of 2 to 50 amino acids.
6. The compound of claim 1 wherein Pep is a an oligopeptide or a
polypeptide comprising a sequence of 2 to 8 amino acids.
7. The compound of claim 1 for catalyzing the stereoselective
phosphorylation of cyclitols.
8. The compound of claim 7 wherein the cyclitol is an inositol
9. The compound of claim 8 wherein the inositol is
myo-inositol.
10. A method of selecting a phosphorylation catalyst of the formula
14wherein R.sub.1 is a lower alkyl; R.sub.2 is an amine protecting
group; and Pep is a peptide comprising a peptide residue including
at least one natural or non-natural amino acid for stereoselective
phosphorylation of a cyclitol comprising: creating a library having
at least one asymmetric phosphorylation catalyst member using an
algorithm; chemically synthesizing the phosphorylation catalyst
member; subjecting a cyclitol or a partially protected derivative
thereof to a phosphorylation reaction with a phosphorylation
reagent in the presence of the phosphorylation catalyst member to
give a corresponding monophosphate compound; and performing a
product assay to determine a stereochemical product composition of
the monophosphate compound.
11. The method of claim 10 wherein R.sub.1.dbd.C.sub.1 to C.sub.6
straight or branched chain alkyl, R.sub.2 is a carbamate, and Pep
is a monopeptide, an oligopeptide or a polypeptide comprising at
least one amino acid.
12. The method of claim 10 wherein the carbamate is selected from
the group consisting of t-butyl carbamate, 9-fluorenylmethyl
carbamate, benzyl carbamate and ortho-nitrobenzyl carbamate.
13. The method of claim 10 wherein R.sub.1 is CH.sub.3 and R.sub.2
is t-butylcarbamate.
14. The method of claim 10 wherein Pep is an oligopeptide or a
polypeptide comprising a sequence of 2 to 50 amino acids.
15. The method of claim 10 wherein the phosphorylation agent is a
dichlorodiakyl phosphate, dichlorodiarylphosphate and derivatives
thereof.
16. The method of claim 10 wherein the phosphorylation agent is
dichlorodiphenyl phosphate.
17. The method of claim 10 wherein the cyclitol monophosphate is an
inositol monophosphate.
18. The method of claim 17 wherein the inositol monophosphate is
(D)-myo-inositol-1-phosphate.
19. The method of claim 17 wherein the inositol monophosphate is
(D)-myo-inositol-3-phosphate.
20. A method of identifying a phosphorylation catalyst to function
as a stereoselective catalyst material for phosphorylation of a
cyclitol comprising: chemically synthesizing at least one
asymmetric phosphorylation catalyst member; subjecting a cyclitol
or a partially protected derivative thereof to a phosphorylation
reaction with a phosphorylation reagent in the presence of the
phosphorylation catalyst member to yield a monophosphate compound;
performing a product assay on the monophosphate compound for
evaluating a stereochemical product composition of the
monophosphate compound; selecting the phosphorylation catalyst of
the formula 15wherein R.sub.1 is a lower alkyl; R.sub.2 is an amine
protecting group; and Pep is a peptide.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/187,208, filed on Jul. 1, 2002, which claims priority
to U.S. Provisional Application Ser. No. 60/302,621, filed on Jul.
2, 2001.
FIELD OF THE INVENTION
[0003] The present invention relates to catalyst materials that
provide regioselective and enantio-selective phosphorylation of
cyclitols, in particular inositols such as myo-inositol.
Specifically, the present invention concerns phosphorylation
catalysts and phosphorylation methods for regio--and
enantioselective synthesis of D-myo-inositol-monophosphate- s.
BACKGROUND OF THE INVENTION
[0004] Cyclitols are cycloalkanes containing one hydroxyl group on
each of three or more ring carbons. The most abundant members of
the cyclitol genus are the inositols
(1,2,3,4,5,6-hexahydroxy-cyclohexanes), the most important
stereoisomer of this family being myo-inositol (I). Myo-inositol
has hydroxyl groups in the 1-, 2-, 3-, and 5-positions of the
cycloaliphatic ring that lie in one side of a stereochemical plane,
and two hydroxyl groups in the 4- and 6-positions that lie on the
other. Phosphorylated derivatives of cyclitols and inositols,
wherein one or more hydroxyl groups are converted to phosphate
monoesters, are generally referred to, respectively, as cyclitol
phosphates or inositol phosphates.
[0005] The biological function of cyclitols, in particular
inositols, depends on both the extent of phosphorylation of the
hydroxyl groups, as well as the position and stereochemistry of the
resulting phosphate functionalities. Complex proteins called
kinases catalyze reactions that put phosphate groups on specific
sites of a substrate. Cellular processes in mammals, including man,
depend, at least in part, on inositol phosphates. Certain inositol
phosphates function as "second messengers", that is, molecules that
provide the means by which neurotransmitters, growth factors or
hormones alter processes inside cells without necessarily
penetrating the cells they affect. D-myo-inositol-1-phosphate is an
important second messenger in cellular signal transduction
pathways. Increased concentrations of these second messengers, in
turn, activate certain enzymatic processes within the cells.
Similarly, some growth factors such as platelet derived growth
factor (PDGF) cause an increased production of inositol phosphates
in the cells they affect. Intracellular concentrations of inositol
phosphates also appear to play a role in the regulation of cell
division and the inflammatory response. Because of the potential
medicinal importance of the natural inositol phosphates, including
its analogs, derivatives and isomers, there has been considerable
interest in these compounds, which is reviewed in the art (Science,
234: 1519 (1986); Scientific American, 253: 142 (1985)).
[0006] Studies pertaining to medicinal application of inositol
phosphates have, however, been limited both by low yields of
insoluble material from natural sources, and the tedious processes
involved in their isolation and purification. This is mainly
attributed to the fact that the inositol substrate offers not only
multiple reactive sites, but also the possibility of enantiomeric
products for each derivatized reactive site. Synthetic methods for
preparing a desired enantiomer, therefore, usually involves either
elaborate protecting-group strategies including use of chiral
auxiliaries, or necessitates laborious isolation, such as for
example, by selective recrystallization or enzymatic resolution.
Practical and efficient synthetic methods for selectively preparing
significant larger amounts in high purity of specific enantiomers
of phosphorylated inositols and their analogs remain a largely
unsolved issue. It is, therefore, desirable to develop efficient
synthetic methods for providing adequate quantities of
enantiomerically pure synthetic insitol phosphates for applications
involving their medicinal use.
SUMMARY OF THE INVENTION
[0007] The present invention concerns the catalytic phosphorylation
of cycloalkanols, including cyclitols in a stereoselective manner
to provide the corresponding cyclitol phosphates. Specifically, the
present invention provides phosphorylation catalysts for the regio-
and enantioselective phosphorylation of cyclitols, particularly
myo-inositol to provide D-myo-inositol-mono-phosphates that are
stereochemically equivalent to the corresponding naturally
occurring compounds. The catalysts of the invention, in terms of
their ability to effect stereoselective phosphorylations at
specific hydroxyl groups in phosphorylate cyclitols, particularly
myo-inositol, mimic the biologically occurring transformation by
the action of complex kinases, and are hence termed to be "kinase
mimics" in analogy to the histidine-dependent class of kinases that
participates in cell-signaling pathways.
[0008] In one aspect, the present invention provides catalyst
materials for the stereoselective phosphorylation of secondary
alcohol functional groups in cyclitols, particularly myo-inositol
in high enantiomeric excess (ee) in high yields relative to
currently employed separation processes. The catalysts of the
present invention comprise of a terminal heterocylic segment that
includes an alkylimidazole moiety that is capable of functioning as
a catalyst for alcohol phosphorylation in substoichiometric ratios
in the presence of a phosphorylating agent. The phosphorylation
catalysts of the invention additionally comprise a low molecular
weight peptide-based segment that is chemically bonded to the
terminal heterocyclic segment described above that renders the
catalysts capable of imparting both high regio- and
stereoselectivity in phosphorylation reactions involving cyclitols.
They phosphorylation catalysts of the present invention are
hereinafter defined as "peptide-based phosphorylation catalysts"
(PBPC's).
[0009] In another aspect, the present invention provides synthetic
methods for the efficient stereoselective (regio- and
enantio-selective) for phosphorylation of secondary alcohols groups
in cyclitols particularly in the naturally occurring compound
myo-inositol to yield corresponding phosphates in high enantiomeric
excess (ee). Specifically, the phosphorylation catalysts of the
present invention provides a stereoselective synthetic method for
obtaining D-myo-inositol-mono-phosph- ates in high enantiomeric
purity and in high yields relative to conventional processes that
are identical to the corresponding naturally occurring
products.
[0010] In yet another aspect, the present invention provides
synthetic methods for creating a synthetic library comprising
low-molecular weight polypeptide phosphorylation catalysts, and a
"parallel reaction" method that enables the identification of
individual members within the library that function as highly
stereoselective catalyst materials for phosphorylation of cyclitol
substrates, particularly myo-inositol. All individual members
within the low-molecular weight polypeptide catalyst library of the
invention comprise a terminal heteroalkyl segment that enable them
to catalyze phosphorylation reactions of cyclitols such as
myo-inositol, either for the same enantiomer or for the opposite
enantiomer of the cyclitol substrate (e.g. myo-inositol) with
respect to that of the original peptide segment in the catalyst.
Individual catalysts within the library of the invention,
therefore, mimic biological enzymes in their ability to effect both
enantioselective mono-phosphorylation of cyclitols such as
myo-inositol providing myo-inositol-monophosphate, and
enantiodivergent phosphorylations, that is, effect divergent
stereoselectivity in the resulting myo-inositol through formation
of highly diverse three-dimensional intermediate structures. Prior
to the present invention, the use of a peptide based
phosphorylation catalysts to effect the stereoselective
phosphorylation for the synthesis of enantioselective and
enantiodivergent myo-inositol-monophosphates were not known.
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1a shows the results of the library screening method
for enantioselectivity of monophosphorylated of protected
myo-inositol.
[0012] FIG. 1b shows the chemical structure of the most selective
PBPC determined by the library screening and parallel reaction and
assay method.
[0013] FIG. 2 shows product identification by the parallel reaction
method of the invention by achiral/chiral HPLC assay.
[0014] FIG. 3 shows the screening data for enantioselective
phosphorylation of protected myo-inositol catalyzed by PBPC's.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The following definitions describe the terms used throughout
the specification and in the claims related to the present
invention.
[0016] As used herein, the term "phosphorylation" means that the
phosphorus in the phosphorylated compound is in the (+5) oxidation
state, P.sup.+5, as part of a phosphate monoester group.
[0017] As used herein "cyclitol monophosphates" or "inositol
monophosphates" denote those phosphorylated derivatives of
cyclitols or inositols that have one hydroxyl group converted to
phosphate monoester.
[0018] As used herein stereoselective refers to the preferential
formation in a chemical reaction of one stereoisomer over
another.
[0019] As used herein enantioselective refers to the preferential
formation in a chemical reaction of one enantiomer over another.
Enantioselectivity and is quantitatively expressed by the
enantiomeric excess (ee).
[0020] As used herein, regioselective refers to a chemical reaction
wherein the product of reaction at one site in the substrate
predominates over the product of reaction at other sites. This
discrimination is also semi-quantitatively referred in terms of the
magnitude of regioselectivity.
[0021] As used herein, enantiodivergent refers to preferential
formation of an enantiomeric product from a reactant substrate that
has an opposite optical rotation with respect to that of that of an
asymmetric reactant or catalyst agent reacting with the reactant
substrate.
[0022] The present invention provides phosphorylation catalysts for
efficient asymmetric phosphorylation of cycloalkanols, in
particular cyclitols such as myo-inositol, with high regio- and
enantioselectivity. The present invention also provides methods
utilizing these catalysts for synthesizing of
myo-inositol-mono-phosphate, including D-myo-inositol-1-phosphate,
which is an important second messenger in cellular signal
transduction pathways. Although the chemical process of the present
invention is directed primarily towards the synthesis of certain
stereoisomers of myo-inositol-monophosphates, this process is
applicable to the regio- and enantioselective synthesis of any
cyclitol phosphate. The general principle of the chemical process
of the present invention is illustrated in detail for
myo-inositol-monophosphates.
[0023] The overall phosphorylation process of the present invention
relies on high regio- and enantioselectivity provided by the
phosphorylation catalysts of the invention, that when reacted in
combination with a phosphorylation agent with a cyclitol such as
myo-inositol, results in a highly stereoselective mono
phosphorylation to give the corresponding
myo-inositol-monophosphate in relatively high yield. The stereo
selective control provided by the phosphorylation catalysts of the
present invention includes both regioselecting (specific position
in the cyclitol ring) and enatio-selectivity preference for a
specific enantiomer the phosphorylation process of the hydroxyl
substituents of cyclitols. Scheme 1, which shows the conversion of
myo-inositol to D-myo-inositol-1-phospha- te (D-I-1P, equation 1)
by the PBPC of the invention. 1
[0024] It should be noted that in conventional nomenclature, the
three adjacent syn hydroxyl groups of myo-inositol are always
designated as occupying the 1, 2, and 3 positions. Since
myo-inositol possesses a plane of symmetry (i.e., it is a meso
isomer), the 1 and 3 positions and the 4 and 6 positions are
identical. When one of these positions is modified, two enantiomers
are possible, and the nomenclature for these compounds can become
ambiguous. For example, the name 1(R)-myo-inositol phosphate
represents the same molecule as 3(S)-myo-inositol phosphate. Thus,
for clarity, all products and synthetic intermediates are referred
to herein by their net optical rotation, namely dextrorotatory (D)
((+) enantiomer use a positive net optical rotation) or
levorotatory (L), ((-) enantiomer wire a negative net optical
rotation) using the numbering system of the desired final
product.
[0025] One or more hydroxyl groups on the cyclitol substrate may,
as is usually desired, be "protected" by one or more "protecting
groups", and the term "protected hydroxyl group" indicates this
type of protected derivatives. During phosphorylation reactions of
the type described herein, protected hydroxyl groups do not react
with the phosphorylating agent under reaction conditions of the
phosphorylation process. The concept of using protecting groups to
mask reactive functional groups is well understood in the field of
synthetic chemistry and is discussed extensively, for example, in
Green, Protective Groups in Organic Synthesis, John Wiley &
Sons, N.Y. (1981).
[0026] The concept that one skilled in the art can prepare a
cyclitol starting material such as for example, an inositol, with
the appropriate number (0 to 5) and types of protecting groups
located on preselected hydroxyl groups is denoted by the
terminology "optionally protected". Suitable protecting groups for
the hydroxyl groups of the cyclitol compounds include, but are not
limited to, ethers, silyl ethers, esters, orthoesters, carbonates,
cyclic acetals, cyclic ketals, cyclic orthoesters, and cyclic
carbonates. Preferred protecting groups include benzyl ethers,
benzoate esters and cyclohexylidene ketals. In a preferred
embodiment, the optionally protected cyclitol is myo-inositol,
wherein the hydroxyl groups in the 2, 4 and 6- positions are
protected with benzyl ether (Bn) by the reaction of myo-inositol
with benzyl bromide (BnBr) to the corresponding benzyl ether
compound 3 as shown by in Scheme 2. 2
[0027] The asymmetric phosphorylation of process of myo-inositol
illustrated in Scheme 1 involves a key step that utilizes the
PBPC's of the invention that function as kinase mimics in effecting
a regio- and enantioselective phosphorylation of the protected
myo-inositol 3 yield phosphorylated compound (-) 4 in a
substantially optically pure form. A subsequent one-step
deprotection of the protected hydroxyl groups affords the
corresponding D-myo-inositol-monophosphate, namely
D-myo-inositol-l-phosphate (D-I-1P). The reaction sequence and
intermediate products involved in this process are illustrated
Scheme 3. 3
[0028] The synthetically obtained D-I-1P by the process illustrated
in Scheme 3 using the (PBPC's) of the present invention is both
optically and structurally (spectroscopically) equivalent to that
of the same compound isolated from natural sources. Thus, although
orders of magnitude less complex in terms of structure than a
macromolecular protein (kinase), the peptide segment of the PBPC's
of the invention provide a substantial control over the product
stereochemistry, with almost total enantioselectivity (>98% ee).
Due to their ability to mimic stereoselective biological enzymes,
low molecular weight phosphorylation catalysts of the invention,
represent a potentially powerful approach to catalytic asymmetric
synthesis of biologically occurring compounds and for mechanistic
modeling of biochemical transformations for their utilization in
medicinal applications.
[0029] The peptide based catalysts of the present invention are
described by the general formula I and comprising a heterocyclic
terminal group, namely an imidazole group and an peptide segment
"Pep". 4
[0030] In one embodiment R.sub.1 is lower alkyl, R.sub.2 amine
protecting group, preferably a carbamate group. Preferred
carbamates include, but are not limited to, t-butyl carbamate
(BOC), 9-fuorenylmethyl carbamate (FMOC, benzyl carbamate (CBz) and
ortho-nitrobenzyl carbamate. Pep is a peptide segment P comprising
a synthetic peptide residue, including but not limited to, an
oligopeptide or a polypeptide residue. In a preferred embodiment,
the peptide residue is a polypeptide comprising from about 2 to
about 50 amino acids, and preferably, between about 2 to about 10
amino acids. In a preferred embodiment, R.sub.1 is methyl (CH.sub.3
or Me) and R.sub.2 is t-butyl carbamate (BOC).
[0031] The low molecular-weight PBPC's of the invention function in
a manner analogous to first step of a biological process comprising
a series of signal transduction cascades involving myo-inositol.
This step involves phosphorylation of histidine, which is effected
by kinase action via a nucleophilic catalytic mechanism. The
proposed catalytic phosphorylation process for cyclitols using the
catalysts of the present invention is shown in Scheme 4. An
inositol substrate, namely protected myo-inositol 3 is catalyzed by
PBPC 1 in the presence of a phosphorylation agent, such as for
example, diphenylchloro-phosphate (DPCP). The PBPC's of the present
invention which are essentially based on modified histidine (His)
residues (e.g., 1) presumably function in a manner analogous to
His-dependent kinases to form a phosphorylated catalyst
intermediate represented by 2. Based on the pendant peptide
sequence, a functionalized, high energy phospho-imidazolium ion is
generated in a chiral environment, that potentially interacts with
multifunctional cyclitol substrates, including myo-inositol in a
site-specific manner. As a result, phosphate transfer to substrate,
such as for example, protected myo-inositol 3 can occur with both
regio- and enantioselectivity to provide the corresponding enantio-
and regiopure phosphate 4, regenerating catalyst 1 and rendering it
available for another catalytic cycle. 5
[0032] The terminal alkylimidazole segment in the PBPC's of the
invention (such as that present in 1), functions efficiently as a
catalyst for phosphorylation of alcohols in substoichiometric
ratios. The proposed was made of action for the PBPC's of the
present invention substantiated by model reactions involving
phosphorylation of cycloaliphatic secondary alcohols by DPCP ,
which occurs with a high degree of enantioselectivity in the
presence of a catalytic amount (2 mol % relative to DPCP) of
N-methylimidazole (NMI) is present in the terminal histidine
segment in the PBPC's. Table 1 summarizes the data from the model
catalytic phosphorylation reactions. As is evident from the model
reactions, relatively high degrees of conversions of (about 66 to
about 95%) is achieved during the catalytic phosphorylation of
several cyclic secondary alcohols (Table 1). Under identical
conditions, the uncatalyzed rate of conversion (phosphotriester
formation in the absence of NMI) is negligible (<5%). Efficient
catalytic turnover in the phosphorylation process of the invention
is achieved by inclusion of a stoichiometric amount of Et.sub.3N as
an additive during the reaction.
1TABLE 1 Amine-based Catalysis of Alcohol Phosphorylation..sup.a 6
7 8 9 .sup.aAnalysis by .sup.1H NMR(400 MHz). Reactions were
quenched after 12 h.
[0033] The low molecular weight PBPC's of the present invention
afford substantially high enantioselectivities in phosphorylation
of cyclitols such as myo-inositol in nonpolar solvents.
Myo-inositol is therefore, protected as the benzylether derivative
3 (Scheme 2), where the benzylether functionalities (i) confer
solubility in non-polar solvents, and (ii) increase the
regioselectivity of the phosphorylation process by reducing the
site-selectivity problem to three unique unprotected hydroxyl
groups.
[0034] The relative stereoselective efficiency of the PBPC's of the
present invention is determined by a library screening method
coupled with a parallel reaction array screening a chemically
synthesized library of PBPC's of the general formula I, wherein the
peptide group is a polypeptide, and is varied as a function of both
the number and sequence of amino acids in the polypeptide chain.
The library screening method of the invention involves a chemically
synthesized library comprising one or more individual library
members that are synthesized on a solid support by standard methods
known in the art using commercially available polystyrene resin
preloaded with the appropriate amino acid. In one embodiment, a
peptide library of about 39 members is generated and subsequently
screened for regio- and enantioselectivity for monophosphorylation
of protected myo-inositol derivative 3. The library is then
examined in conjunction with the parallel reaction assay, wherein
39 independent phosphorylation reactions (one for each library
member) of protected myo-inositol derivative 3 by individual
library members is carried out under substantially identical
conditions (0.degree. C., 2 mol % unpurified PBPC in toluene
(PhCH.sub.3) solvent). FIG. 1 shows one example of the parallel
screening method of the present invention wherein the
enantio-selectivity for phosphorylation of the 1- versus 3-hydroxyl
positions of the protected myo-inositol derivative 3 is used to
identify the polypeptide segment in the PBPC that provides the
highest regio- and enantioselectivity in the phosphorylated product
(FIG. 1a). A two-stage achiral/chiral HPLC assay is then performed
on the reaction mixtures to determine the overall product
distribution. FIG. 2 shows the product identification assay by the
achiral/chiral HPLC assay method. In the example shown, PBPC 6
comprising a pentapeptide shows the highest enantioselectivity
(FIG. 1b). It is evident from the screening data (FIG. 1a) that
each PBPC catalyst in the library affords a different level of
enantioselectivity for the catalytic phosphorylation, underscoring
the influence of peptide secondary structure in the PBPC's on the
stereochemical outcome in the phosphorylated myo-inositol product.
Pentapeptide 6, in its unpurified form provides the phosphorylated
myo-inositol derivative (-)-4 (Scheme 4) with good
enantioselectivity (90% ee) under the parallel screen
conditions.
[0035] The PBPC catalyst comprising a peptide segment identified to
provide the highest regio- and enantioselectivity by the screening
method of the invention described herein, such as for example
PBPC6, is then re-synthesized, purified to chromatographic
homogeneity and utilized in a PBPC catalyzed asymmetric total
synthesis of myo-inositol-monophosphate. In one embodiment, the
PBPC catalyst 6 comprising the pentapeptide segment peptide is used
in the synthesis of (D)-I-1P as illustrated in Scheme 2. Treatment
of myo-inositol derivative 3 with DPCP and Et.sub.3N (1 equiv.), 2
mol % purified 6 in PhCH.sub.3 (0.degree. C.) provides the
corresponding monophosphate (-)-4 as a single enantiomer (>98%
ee by chiral HPLC, with about 70% conversion and about 58% isolated
yield). Optically pure (-)-4 then converted to D-I-1P (which may be
also represented as (+)-I- 1P) in a single step by deprotection of
the protected hydroxyl groups in about 73% isolated yield. The
optical rotation of enantiomerically pure D-I-1P compound
synthesized by the catalytic process of the present invention is
identical to the naturally occurring compound (synthetic:
[.alpha.].sub.D+3.5 c 1.0, pH=9: natural: [.alpha.].sub.D+3.5 c
1.0, pH=9). The catalytic process of the invention is relatively
more efficient for obtaining D-I-1P than its isolation from natural
sources, providing >150 mg of synthetic D-I-1P from about 500 mg
of myo-inositol in a laboratory scale process. It is therefore,
readily amenable to scale-up in a commercial process, both due to
its simplicity in terms of the number of individual steps involved,
and the high enantiomeric purity and relative yields of the
product.
[0036] The PBPC catalysts of the invention can also be optimized to
effect an enantiodivergent phosphorylation of cyclitols, in
particular, myo-inositol. They are, therefore, capable of
functioning in similar manner to enzymes that perform
enantiodivergent chemical transformations in biologic systems. This
characteristic is particularly noteworthy in the case of enzymes
that perform enantiodivergent chemistry is a biological
environment, since they are composed almost exclusively of L-amino
acids; completely enantiomeric enzymes composed entirely of D-amino
acids, are relatively found in nature. In one embodiment, the PBPC
catalyst of the present invention comprising a pentapeptide segment
can be used in a catalytic phosphorylation reaction of a cyclitol,
such as for example myo-inositol that is highly enantioselective
for the opposite enantiomer of the inositol substrate with respect
to the original peptide segment in the PBPC. A preferred embodiment
of an enantiodivergent phosphorylation of myo-inositol with the
PBPC catalyst of the present invention is shown in Scheme 5. The
protected derivative of myo-inositol 2 is reacted with a
phosphorylating agent (DPCP) in the presence of PBPC 24 to yield
the corresponding monophosphate derivative 4(3-P), which is
subsequently subjected to a deprotection reaction to yield the
enantiodivergent monophosphate D-1-3P (Scheme 5). 10
[0037] The PBPC's providing the highest regio- and enantiodivergent
cyclitol monophosphate products, particularly
myo-inositol-monophosphate is determined by the library screening
method and "parallel reaction" method of the present invention
described herein, whereby highly enantioselective PBPC's are by
screening of a combination of random and focused libraries. FIG. 3
shows one example of the random and focused library screening
method of the invention. The initial screen (FIG. 3A) of small
peptide catalysts for asymmetric phosphorylation of protected
myo-inositol substrate 2 (Scheme 5) is based on 39 peptides (tetra-
through octapeptides) that contain a L-.pi.(Me)-histidine
nucleophilic residue. A number of PBPC's that selectively
phosphorylate the 1-position of substrate 2 to give 4(1-P) are
isolated within this library, as well as others that are selective
for the enantiotopic 3-position, albeit with relatively lower
selectivity. The choice of individual library members forming the
initial 39-member is primarily based on synthetic sequences that
are soluble in organic solvents. The results of the expanded screen
are shown in FIG. 3B, wherein unpurified peptides were screened at
room temperature.
[0038] PBPC's from both the initial and expanded screens (peptides
1-136) are selected on the both on the basis of sequences that are
biased to form .beta.-tums and .beta.-hairpins in organic solvents,
and on breadth of diversity in the amino acid sequences. To achieve
diverse sequences, a randomization algorithm is utilized to afford
sequences that are, in principle, unrelated. In one preferred
embodiment, PBPC 5 comprising a pentapeptide is chosen as the core
structure, following which a letter for each of 16 amino acid
monomers is then assigned. The algorithm subsequently delivered 80
random sets of three-letter combinations. These are inserted into
the core structure 5, following which individual members are
synthesized for the library screening and parallel assay method of
the invention. 11
[0039] The results of the expanded screen were striking in that the
distribution of catalysts that were selective for the enantiotopic
1- and 3- positions are almost statistical. For example, in the
expanded screen two new sequences 6 and 7 (FIG. 3) provide the
enantiodivergent product 4(3-P) in >55% ee; similarly, two other
sequences are selective for the enantiotopic 4(1-P) in >55% ee.
Since the extent of enantioselectivity for the formation of the
phosphorylated product in these desymmetrization reactions is
related to the overall conversion of the reaction be this issue,
overinterpretation of small differences in the ee of the isolated
4(3-P) is avoided. Although the conditions utilized in the library
screening method of the present invention is designed to produce
the protected myo-inositol-monophosphate at about 70% conversion
for the highly enantioselectivive members, less selective members
of the library also distribute themselves into enantiodivergent
groups (83 selective for 4(1-P), 51 selective for 4(3-P)) (FIGS. 3A
and 3B). In a preferred embodiment, PBPC's 6 and 7 (FIG. 3) are
chosen for the selective catalytic phosphorylation process for
obtaining 4(3-P), since they are both moderately selective for
4(3-P). PBPC's 6 and 7 are in the .beta.-tum family, in comparison
to PBPC 1, which has its origin in the random library. A focused
library 8 is then designed around these selected individual
members.
[0040] In one embodiment, the L-Hyp residue (R.sub.3 in FIG. 3) is
exchanged with L-Pro and BnHyp in a 42-member library. Further, the
geminal substitution in the i+2 position is varied
.alpha.-amino-.alpha.-methylalanine (Aib) and spirocyclic groups.
Additionally, least eight other residues are appended in the i+3
position we explored 8 other residues to achieve a 42-member
library. The library screening data for the individual members is
shown in FIG. 3C and in Table 2.
[0041] From individual library members (PBPC's) that are selective
for the enantiotopic 4(3-P) (Scheme 5), the following trends are
summarized (Table 2): (1) A 5-membered spirocyclic residue in the
i+2 position contributes to catalyst selectivity (PBPC's 10, 15 and
20) (2) a t-BuTyr at the +3 position provides increased selectivity
(PBPC's 13, 18 and 23).
2TABLE 2 Selected Data from Focused.sup.a 12 .sup.aScreen was
performed with unpurified catalysts (2.5 mol %, 25.degree. C.),
uniformly quenched after 6 h. See Supporting Information
[0042] The trends obtained from the library screening assay of the
present invention can be used to optimize the functional groups at
the i+3 position. In the embodiment whose library screening results
are shown in Table 2, it can be concluded that PBPC's comprising a
5-membered ring in combination with t-BuTyr at the i+3 position is
likely to yield a superior catalyst in terms of selectivity. Based
on such analysis, a non-library member PBPC 24 (Table 2) prepared
by independent synthesis exhibits high selectivity for the
formation of 4(3-P), affording the product in about 94% ee at about
70% conversion even under the un-optimized conditions of the
screen. The optimized PBPC 24 can be used for the total synthesis
of D-myo-inositol-3-phosphate (D-I-3P) as shown in Scheme 6, in a
manner analogous to the synthesis of enantiomeric D-I-1P (Scheme
3). In one example, desymmetrization of substrate 2 provides 4(3-P)
with almost complete enantiopurity (>98% ee, about 56% isolated
yield) using PBPC 24 under optimized conditions (2.5 mol %,
0.degree. C., 4 h). The phosphorylated intermediate 4(3-P) is
subsequently deprotected in a single step to give synthetic D-I-3P,
whose characteristics match literature values.
[0043] The library screening assay of the present invention, by
using a combination of random and focused libraries, enables the
identification of low molecular-weight PBPC's (small molecule
peptides) that are capable of selecting for specific positions for
phosphorlyation of cyclitols. Specifically, such PBPC's are capable
of selecting for either the 1-position or the enantiotopic
3-position during catalytic phosphorylation of an inositol
derivative.
[0044] The library screening assay of the present invention can be
used for the identification of catalysts that allow for enantio-
and regioselective functionalization of other polyfunctionalized
molecules, including biologically important ones, that may be of
importance in medicinal applications.
EXAMPLES
[0045] General Procedures. Proton NMR spectra were recorded on
Varian 400 or 300 spectrometers. Proton chemical shifts are
reported in ppm (.delta.) relative to internal tetramethylsilane
(TMS, .delta. 0.0) or with the solvent reference relative to TMS
employed as the internal standard (CDCl.sub.3, .delta. 7.26 ppm;
d.sub.6-DMSO, .delta. 2.50; C.sub.6D.sub.6, .delta. 7.16 ppm;
D.sub.2O, .delta.4.79). Data are reported as follows: chemical
shift (multiplicity.[singlet (s), doublet (d), triplet (t), quartet
(q), and multiplet (m)], coupling constants [Hz], integration).
Carbon NMR spectra were recorded on Varian 400 (100 MHz) or 300 (75
MHz) spectrometers with complete proton decoupling. Carbon chemical
shifts are reported in ppm (.delta.) relative to TMS with the
respective solvent resonance as the internal standard (CDCl.sub.3,
.delta. 77.0). Phosphorous NMR spectra were recorded on Varian 400
(162 MHz) spectrometer with complete proton decoupling. Phosphorous
chemical shifts are reported in ppm (.delta.) relative to a 85%
H.sub.3PO.sub.4 external standard. NMR data were collected at
25.degree. C., unless otherwise indicated. Infrared spectra were
obtained on a Perkin-Elmer Spectrum 1000 spectrometer. Analytical
thin-layer chromatography (TLC) was performed using Silica Gel 60
F254 precoated plates (0.25 mm thickness). TLC R.sub.f values are
reported. Visualization was accomplished by irradiation with a UV
lamp and/or staining with KMnO.sub.4 or cerium ammonium molybdenate
(CAM) solutions. Flash column chromatography was performed using
Silica Gel 60A (32-63 .mu.m). Optical rotations were recorded on a
Rudolf Research Analytical Autopol IV Automatic polarimeter at the
sodium D line (path length 50 mm). Elemental analyses were
performed by Robertson Microlit (Madison, N.J.). High resolution
mass spectra were obtained at the Mass Spectrometry Facilities
either of the University of Illinois (Urbana-Champaign, Ill.), or
Boston College (Chestnut Hill, Mass.). The method of ionization is
given in parentheses.
[0046] Analytical and preparative reverse phase and normal phase
HPLC were performed on a Rainin SD-200 chromatograph equipped with
a single wavelength UV detector (214 nm or 254 nm). Analytical
normal phase HPLC was performed on a Hewlett-Packard 1100 Series
chromatograph equipped with a diode array detector (214 nm and 254
nm).
[0047] All reactions were carried out under an argon or nitrogen
atmosphere employing oven- and flame-dried glassware. All solvents
were distilled from appropriate drying agents prior to use.
Diphenyl chlorophosphate was distilled prior to use and stored in a
Schienk tube for no more than 2 weeks
2,4,6-Tri-O-berizyl-myo-inositol (3) was prepared according to a
prior art method (Billington et al., J. Chem. Soc. Perkin Trans. I,
(1989), 1423).
Example 1
[0048] Phosphorylation of Secondary Alcohols (Model Reactions)
[0049] The phosphorylation of alcohols in Table 1 was carried out
in the following manner: Cyclopentanol (0.060 mL, 0.66 mmol) was
dissolved in 25 mL of toluene and an aliquot of N-methyl imidazole
in CH.sub.2Cl.sub.2 (50 .mu.L, 0.017 mmol, 2.5 mol %) was
delivered. Triethylamine (0.185 mL, 1.33 mmol) was added followed
by diphenyl chlorophosphate (0.275 mL, 1.33 mmol). After 12 h the
reaction was quenched with 2 mL of methanol and concentrated under
reduced pressure. The compound was purified by silica gel flash
chromatography, eluting with a gradient of hexanes to 15% ethyl
acetate/hexanes, to yield 0.158 g (75% yield) of alcohol Diphenyl
cyclopentane phosphate as a viscous liquid.
Diphenyl Cyclopentane Phosphate
[0050] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.35-7.31 (m, 5H),
7.23-7.16 (m, 5H), 5.14 (m, 1H), 1.94-1.69 (m, 6H), 1.65-1.54 (m,
2H);
[0051] .sup.13C NMR (CDCl.sub.3 100 MHz) .delta. 150.4 (d, J=7.6
Hz), 129.5, 124.9, 119.9 (d, J=4.6 Hz), 83.3 d, J=6.9 Hz), 33.9 (d,
J=5.3 Hz), 22.9;
[0052] .sup.31P NMR (CDCl.sub.3, 162 MHz) .delta. -13.8;
[0053] IR (film, cm.sup.-1) 3490, 3062, 2968, 1596, 1486, 1287;
[0054] TLC R.sub.f 0.23 (20% ethyl acetate/hexanes);
[0055] Anal. Calcd. for C.sub.17H.sub.19O.sub.4P: C, 64.15; H,
6.02; P, 9.73. Found: C, 64.23; H, 6.02; P, 9.79;
[0056] Exact mass calcd for [C.sub.17H.sub.19O.sub.4P+Na]+requires
m/z 341.0919. Found 341.0919 (ESI+).
Diphenyl Cycloheptane Phosphate
[0057] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.36-7.3.1 (m,
4H), 7.23-7.15 (m, 6H), 4.80 (m, 1H), 1.99 (m, 2H), 1.82 (m, 2H),
1.68-1.50 (m, 6H), 1.39 (m, 2H);
[0058] .sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 150.6, 129.5,
125.0, 120.0 (d, J=5.3 Hz), 82.2 (d, J=6.9 Hz), 35.4 (d, J=4.6 Hz),
28.0, 22.1;
[0059] .sup.31P NMR (CDCl.sub.3, 162 MHz) .delta. -12.0;
[0060] IR (film, cm.sup.-1) 3496, 3069, 2936, 1941, 1590, 1487,
1288;
[0061] TLC R.sub.f 0.38 (20% ethyl acetate/hexanes);
[0062] Anal. Calcd. for C.sub.19H.sub.23O.sub.4P: C, 65.89; H,
6.69; P, 8.94. Found: C, 65.9.6; H, 6.49; P, 8.85;
[0063] Exact mass calcd for [C.sub.19H.sub.23O.sub.4P+Na]+requires
m/z 369.1232. Found 369.1217 (ESI+).
Diphenylcyclooctane Phosphate
[0064] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.35-7.10 (m,
10H), 4.79 (m, 1H), 1.97-1.85 (m, 4), 1.72-1.43 (m, 10H);
[0065] .sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 150.5 (d, J=6.9
Hz), 129.5, 125.0, 120.0 (d, J=4.6 Hz), 82.3 (d, J=6.9 Hz), 32.4
(d, J=3.8 Hz), 27.3, 24.9, 22.2;
[0066] .sup.31P NMR (CDCl.sub.3, 162 MHz) .delta. -11.9;
[0067] IR (film, cm.sup.-1) 3478, 3068, 2917, 1948, 1589, 1489,
1284;
[0068] TLC Rf 0.41 (20% ethyl acetate/hexanes);
[0069] Anal. Calcd. for C.sub.20H.sub.25O.sub.4P: C, 66.66; H,
6.99; P, 8.59. Found: C, 66.53; H, 6.82; P. 8.30;
[0070] Exact mass calcd for [C.sub.20H.sub.25O.sub.4P+Na]+requires
m/z 383.1388. Found 383.1395 (ESI+).
Example 2
PBPC Peptide Synthesis
[0071] Peptides were synthesized on solid support using
commercially available Wang polystyrene resin preloaded with the
appropriate amino acid. Couplings were performed using 4 equiv.
amino acid derivative, 4 equiv. HBTU, and 3 equiv. Hunig's base in
DMF, for 3 h. Deprotections were performed using 20% piperidine in
DMF for 20 mm (to minimize diketopiperazine formation, dipeptides
were deprotected using 50% piperidine in DMF for 5 min). Peptides
were cleaved from solid support using a mixture of
MeOH:DMF:NEt.sub.3 (9:1:1) for 4 d. The peptides were characterized
by electrospray mass spectrometry and used in parallel reaction
screens without further purification. Peptide 6 which proved
selective for the desymmeterization of triol (3) was purified by
reverse phase HPLC techniques. Preparative HPLC was performed using
a reverse phase RP-18 X Terra (Waters) column, eluting with 57-73%
methanol in water, at a flow rate of 4.15 mL/min. The purity was
checked by analytical HPLC under similar conditions.
[0072] Data for Peptide 6
[0073] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.92 (s, 1H), 7.60
(d, J=7.0 Hz, 1H), 7.49 (d, J=8.1 Hz, 1H), 7.33-7.09 (m, 24H), 6.75
(s, 1H), 6.66 (s, 1H), 5.25 (d, J=-8.1 Hz, 1H), 4.94 (m, 2H), 4.69
(m, 1H), 4.51 m, 3H), 4.32 (m, 1H), 3.68 (s, 3H), 3.51 (s, 3H),
3.15-2.81 (m, 6H), 2.44 (d, J=4.8 Hz, 2H), 1.42 (s, 9H), 1.35 (s,
9H), 1.31 (d, J=7.3 Hz, 3H);
[0074] Low resolution mass calcd. for
[C.sub.60H.sub.72N.sub.10O.sub.11+H]- +requires m/z 1109.3. Found
1109.5 (ESI+);
[0075] Exact Mass calcd for
[C.sub.60H.sub.72N.sub.10O.sub.11-C.sub.19H.su- b.15(trityl)+2H]
+requires m/z 867.4365. Found 867.4358 (ESI.+-.);
[0076] HPLC retention time 36.2 mm on a RP-18 X Terra (Waters)
column eluting with a gradient of 57-73% methanol/water over 40 mm,
at a flow rate of 0.2 mL/min.
3TABLE 1a Data for Peptide Libraries Peptide Sequence Calcd M + H
Obs. M + H ee % of 4 A1 BOC-Pmh-D-Pro-Aib-Phe-OMe 613.34 613.33 -5
A2 BOC-Pmh-D-Pro-Pro-Phe-OMe 625.74 625.87 7 A3
BOC-Pmh-D-Val-D-Val-D-Pro-GIy-Leu-Val-D-Val-OMe 947.59 947.59 14 A4
Boc-Pmh-D-Pro-Hfe-Phe-D-Phe-OMe 836.99 836.22 16 A5
BOC-Pmh-D-Pro-D-Pip-Aib-Phe-OMe 627.74 627.87 10 A6
BOC-Pmh-D-Pro-Phe-Hfe-D-Phe-OMe 836.99 836/30 18 A7
BOC-Pmh-D-Pro-Hfe-Cha-D-Phe-OMe 843.03 842.39 12 A8
BOC-Pmh-D-Pro-Cha-Phe-D-Phe-OMe 829.01 828.37 14 A9
BOC-Pmh-D-Pro-Hfe-Phe-D-Phe-Phe-OMe 984.16 938.42 11 A10
BOC-Pmh-DPro-2-amino-2-indan-2-carboxylic acid-Hfe-Phe-OMe 849.00
848.25 10 A11 BOC-Pmh-D-Pro-1-amino-1-cyclooctane carboxylic
acid-Phe-OMe 681.84 681.27 9 A12
BOC-Pmh-D-Pip-1-amino-1-cyclopentane carboxylic acid-Hfe-Phe-OMe
814.98 814.53 12 A13 BOC-Pmh-D-Pip-Hfe-Phe-Phe-OMe 851.01 850.23 7
A14 BOC-Prnh-D-Pip-Aib-Cha-Phe-OMe 780.97 780.33 13 A15
BOC-Pmh-D-Pro-1-amino-1-cyclooctane carboxylic acid-Phe-OMe 681.84
681.27 -3 A16 BOC-Pmh-D-Pro-1-amino-1-cyclohexane carboxylic
acid-Leu-Phe-OMe 766.38 766.38 17 A17 BOC-Pmh-D-Pro-1-amino-1-cycl-
ohexane carboxylic acid-Phe-OMe 766.38 766.38 3 A18
BOC-Pmh-D-Pro-Hfe-D-Phe-Phe-OMe 836.99 836.27 -26 A19
BOC-Pmh-D-Pip-Hfe-D-Phe-OMe 703.84 703.24 16 A20
BOC-Pmh-D-Pip-1-amino-1-cyclooctane carboxylic acid-Phe-OMe 695.87
695.32 12 A21 BOC-Pmh-D-Pro-2-amino-2-indan
carboxylicacid-Phe-Phe-OMe 834.98 834.26 3 A22
BOC-Pmh-D-Pfo-1-amino-1-cyclooctane carboxylic acid-Chg-Phe-OMe
821.04 820.38 4 A23 BOC-Pmh-D-Pro-2-amino-2-indan carboxylic
acid-Phe-OMe 687.81 687.23 1 A24
BOC-Pmh-D-Pro-1-amino-1-cyclohexane carboxylic acid-Cha-Phe-OMe
807.01 806.37 7 A25 BOC-Pmh-Thr(But)-D-Glu(OBut)-Hfe-Ala-OMe 859.04
859.14 -9 A26 BOC-Pmh-D-Pro-Gly-1-amino-1-cyclohexane-Phe-OMe
710.83 710.25 -10 A27 BOC-Pmh-D-Val-Aib-D-Ala-Ala-OMe 610.73 611.08
-25 A28 BOC-Pmh-D-Glu(OBut)-Aib-Cha-Ala-OMe 778.96 779.12 5 A29
BOC-Pmh-Asn(Trt)-His(.pi.Bn)-Asp-OBut-Ala-OMe 1110.28 1110.11 90
A30 BOC-Pmh-Aib-Chg-Phe-Ala-OMe 726.88 727.14 41 A31
BOC-Pmh-D-Pip-1-amino-1-cyclohexane carboxylic acid-Hfe-Phe-OMe
829.02 828.28 16 A32
Boc-Pmh-Thr(OBut)-D-Val-His(Trt)-D-Phe-D-Val-Thr(OBu- t)-Ile-OMe
1436 1436 -25 A33 BOC-Pmh-His(.pi.Bn)-D-Glu(OBut)-Aib-Al- a-OMe
853.00 853.17 -10 A34 BOC-Pmh-Leu-Ile-Phe-Ala-OMe 728.89 729.15 8
A35 BOC-Pmh-D-Val-D-Glu(OBut)-Asp-OBut-Ala-OMe 810.95 811.12 25 A36
BOC-Pmh-Phe-D-Glu(OBut)-Asn(Trt)-Ala-OMe 1044.21 1044.15 -14 A37
BOC-Pmh-Asn(Trt)-D-Ala-D-Glu(OBut)-Ala-OMe 968.12 968.12 -2 A38
BOC-Pmh-Asp-OBut-Leu-D-Glu(OBut)-Ala-OMe 824.97 825.17 -16 A39
BOC-Pmh-Ile-Cha-Aib-Ala-OMe 706.89 707.16 29
Example 3
Phosphorylation of Triol 3
[0077] Standard Conditions for Phosphorylation Employing DMAP
[0078] Triol (3) (0.025 g, 0.057 mmol) was dissolved in 1.5 mL of
CH.sub.2Cl.sub.2 and an aliquot of a DMAP solution in
CH.sub.2Cl.sub.2 (50 .mu.L, 0.0028 mmol, 5.0 mol %) was added.
Triethylamine (9.0.mu.L, 0.065 mmol) was then introduced followed
by diphenyl chlorophosphate (0.012 mL, 0.058 mmol). After 12 h the
reaction was quenched with 0.5 mL of methanol and concentrated
under reduced pressure. The starting material, the 1- and 5-mono
phosphate products and the 1,3- and 1,5-diphosphate products were
separated by preparative HPLC employing a normal phase YMC-Pack
PVA-Sil NP column, eluting with a gradient of 0-6.5%
2-propanol/hexanes over 40 min, at a flow rate of 10 mL/min (see
diagram 1 for HPLC trace). The five compounds were identified and
characterized by .sup.1H NMR, .sup.31P NMR and Mass
Spectrometry.
Example 4
[0079] Standard Conditions for Phosphorylation Using PBPC's
[0080] Parallel screening of the peptide catalysts in Table 1a were
performed using either 25 mg or 50 mg of triol (3), as exemplified
by the following experimental procedure. Triol 3 (0.050 g, 0.1
mmol) was dissolved in 2.5 mL of toluene. Each catalyst to be
screened was dissolved in CH.sub.2Cl.sub.2 and an aliquot (50
.mu.L, 0.0027 mmol, 2.5 mol %) was added to the reaction vessel.
Triethylamine ( 0.021 mL, 0.15 mmol) was then added followed by
diphenyl chlorophosphate (0.030 mL, 0.14 mmol). After 4 h the
reactions were filtered to remove triethylamine salts, quenched
with 1 mL of methanol and concentrated under reduced pressure. The
crude reaction mixture was purified by preparative HPLC as reported
above. The myo-inositol 1-phosphate peak was collected and the
enantiomers were separated by chiral HPLC.
Example 5
[0081] Enantioselective Phosphorylation Using PBPC 6 and Product
Isolation
[0082] Triol 3 (0.501 g, 1.11 mmol) was dissolved in 28 mL of
toluene and an aliquot of peptide 6 in CH.sub.2Cl.sub.2 (0.50 mL,
0.028 mmol, 2.5 mol %) was delivered. The reaction was then cooled
to 0.degree. C. and triethylamine (0.170 mL, 1.22 mmol) was added
followed by diphenyl chlorophosphate (0.230 mL, 1.11 mmol) which
had been cooled to 0.degree. C. After 2 h and 4 h additional
triethylamine (0.085 mL, 0.61 mmol) and diphenyl chlorophosphate
(0.115 mL, 0.55 mmol) were added. After 6 h the reaction was
filtered to remove triethylamine salts, quenched with 4 mL of
methanol, and concentrated under reduced pressure. Diol X was
purified using silica gel flash chromatography eluting with 25%
ethyl ether/toluene to yield 0.438 g (58% yield) of (4), which upon
trituration with hexanes became a white solid.
(-)-2,4,6-Tri-O-benzyl-myo-inositol 1-phosphate (4)
[0083] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.38-7.14 (m,
25H), 4.91-4.63 (m, 6H), 4.59 (m, 1H), 4.25 (t, J=2.6 Hz, 1H), 3.95
(t, J=9.5 Hz, 1H), 3.72-3.55 (m, 3H), 2.42 (d, J=1.2 Hz, 1H), 2.21
(d, J=2.6 Hz, 1H);
[0084] .sup.13C NMR (CDCl.sub.3, 100 MHz) .delta. 150.3, 150.2,
138.3 (d, J=7.6 Hz), 138.0, 129.6 (d, J=6.9 Hz), 128.4, 128.3,
128.2, 127.9, 127.8, 127.8, 127.6 (d, J=10.7 Hz), 127.3, 125.3 (d,
J=14.5 Hz), 120.0 (d, 3=4.6 Hz), 119.8 (d, J=5.3), 80.9, 80.1 (d,
J=6.1 Hz), 79.8 (d, J=6.9 Hz), 78.9, 75.4, 75.2, 75.0, 74.7,
71.8;
[0085] .sup.31P NMR (CDCl.sub.3, 162 MHz) .delta. -11.7;
[0086] IR (film, cm.sup.-1) 3402, 2099, 1646, 1485, 1282;
[0087] TLC R.sub.f0.33 (50% ethyl ether/toluene);
[0088] [.alpha.].sub.D=-3.2 (1.0, CH.sub.2Cl.sub.2, at 99% ee);
[0089] Anal. Calcd. For C.sub.39H.sub.39O.sub.9P: C, 68.61; H,
5.76; P, 4.54. Found: C, 68.56; H, 5.51; P, 4.36;
[0090] Exact mass calcd for [C.sub.39H.sub.39O.sub.9P+Na]+requires
m/z 705.2229. Found 705.2253 (ESI+);
[0091] HPLC retention time. 29.6 min employing a normal phase
YMC-Pack PVA-Sil NP column, eluting with a gradient of hexanes to
6.5% 2-propanol/hexanes over 40 min, at a flow rate of 10
mL/min;
[0092] Assay of enantiomeric purity. Enantiomers of 4 were
separated utilizing a Chiracel OD column (Alltech), eluting with
30% ethanol/hexanes at a flow rate of 0.5 mL/min. Retention times:
myo-Inositol 1-phosphate: R.sub.t(L)=11.5 min; R.sub.t(D)=12.7
min.
2,4,6-Tri-O-benzyl-myo-inositol
[0093] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.41-7.30 (m,
15H), 4.85 (m, 6H), 4.02 (t, J=2.7 Hz, 1H), 3.61 (m, 5H);
[0094] Low resolution mass calcd for
[C.sub.27H.sub.30O.sub.6+Na]+requires m/z 473.2. Found 473.3
(ESI+);
[0095] HPLC Retention time. 28.5 min employing a normal phase
YMC-Pack PVA-Sil NP column, eluting with a gradient of hexanes to
6.5% 2-propanol/hexanes over 40 min, at a flow rate of 10
mL/min.
2,4,6-Tri-O-benzyl-myo-inositol 1,5-diphosphate
[0096] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.40-6.98 (m,
35H), 4.86-460 (m, 8H), 4.31 (t, 3=2.6 Hz, 1H), 4.20 (t, J=9.5 Hz,
1H), 3.95 (t, J=9.5 Hz, 1H), 3.65 (m, 1H), 2.06 (d, J=5.1 Hz);
[0097] .sup.31P NMR (CDCl.sub.3, 162 MHz) .delta. -11.9, -11,9;
[0098] Low resolution mass calcd for
[C.sub.51H.sub.48O.sub.12P.sub.2+Na]+- requires m/z 937.2. Found
936.7 (ESI+);
[0099] HPLC Retention time. 33.9 min employing a normal phase
YMC-Pack PVA-Sil NP column, eluting with a gradient of hexanes to
6.5% 2-propanol/hexanes over 40 min, at a flow rate of 10
mL/min.
2,4,6-Tri-O-benzyl-myo-inositol 1,3-diphosphate
[0100] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.37-7.09 (m,
35H), 4.76 (d, J=11.4 Hz, 2H), 4.68 (d, J=11.4 Hz, 2H), 4.62 (m,
2H), 4.50 (s, 2H), 4.49 (t, J=2.4 Hz, 1H), 3.97 (t, J=9.5 Hz, 2H),
3.62 (t, J=9.2, Hz, 1H);
[0101] .sup.31P NMR (CDCl.sub.3, 162 MHz) .delta. -12.0;
[0102] Low resolution mass calcd for
[C.sub.51H.sub.48O.sub.12P.sub.2+Na]+- requires m/z 937.2. Found
936.7 (ESI+);
[0103] HPLC Retention time. 34.8 min employing a normal phase
YMC-Pack PVA-Sil NP column, eluting with a gradient of hexanes to
6.5% 2-propanol/hexanes over 40 min, at a flow rate of 10
mL/min.
2,4,6-Tri-O-benzyl-myo-inositol 5-phosphate
[0104] .sup.1H NMR (CDCl.sub.3, 400 MHz) .delta. 7.42-7.07 (m,
25H), 4.87-4.64 (m, 7H), 3.99 (t, J=2.9 Hz, 1H), 3.90 (t, J=9.5 Hz,
2H), 3.62 (dd, J=2.6 Hz, 9.5 Hz, 2H);
[0105] .sup.31P NMR(CDCl.sub.3, 162 MHz) .delta. -11.7;
[0106] Low resolution mass calcd for
[C.sub.39H.sub.39O.sub.9P+Na]+require- s m/z 705.2. Found 705.0
(ESI+);
[0107] HPLC Retention time. 36.2 min employing a normal phase
YMC-Pack PVA-Sil NP column, eluting with a gradient of hexanes to
6.5% 2-propanol/hexanes over 40 min, at a flow rate of 10
mL/min.
Example 6
(D)-myo-Inositol 1-Phosphate Biscyclohexylamine Salt
[0108] Cleavage of both the phenyl and benzyl groups was achieved
by a modification of a known procedure (Billington et al., J. Chem.
Soc. Perkins Trans. I, (1989), 1423). Ammonia (20 mL) was condensed
into 10 mL of THF at -77.degree. C. under an atmosphere of argon.
Lithium wire 0.5 cm was introduced into the solution, causing it to
turn deep blue. A solution of diol 4 (0.90 g, 1.3 mmol) in THF (4
mL) was then added drop-wise until the solution became clear.
Another piece of lithium wire (0.5 cm) was added and this titration
procedure was continued until all the substrate was added. Lithium
wire (0.5 cm) was then added and the reaction was stirred for 20
min, upon which time it was quenched with small pieces of ice. The
solution was slowly warmed to room temperature and the ammonia was
evaporated under a stream of argon. The resulting solids were taken
up in 4 mL of H.sub.2O and passed through a column of Dowex
500WX2-200 ion-exchange resin eluting with H.sub.2O. The acidic
fractions were collected and stirred with 3 mL of cyclohexylamine
for 1 hr. The H.sub.2O was removed by lyophilization to yield 0.58
g (96% yield) of myo-Inositol 1-phosphate biscyclohexylamine salt,
which was recrystallized from acetone/water.
[0109] .sup.1H NMR (D.sub.2O, 400 MHz) .delta. 4.06 (t, J=2.7 Hz,
1H), 3.73 (m, 1H), 3.58 (t, J=9.5 Hz, 1H), 3.44 (m, 2H), 3.17 (t,
J=9.2 Hz, 1H), 2.98 (m, 2H), 1.83-0.98 (m, 20H);
[0110] .sup.3P NMR (D.sub.2O, 162 MHz) .delta. 4.37;
[0111] [.alpha.].sub.D=3.5 (1.0, H.sub.2O, at pH 9).
* * * * *