U.S. patent application number 12/584311 was filed with the patent office on 2010-01-07 for process for preparing forms of atorvastatin calcium substantially free of impurities.
This patent application is currently assigned to Teva Pharmaceuticals USA, Inc.. Invention is credited to Nina Finkelstein.
Application Number | 20100000302 12/584311 |
Document ID | / |
Family ID | 35545174 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100000302 |
Kind Code |
A1 |
Finkelstein; Nina |
January 7, 2010 |
Process for preparing forms of atorvastatin calcium substantially
free of impurities
Abstract
The preparation of atorvastatin calcium epoxide dihydroxy (AED)
is described. AED can be used as a standard or marker in
determining the amount of AED in a sample. AED can therefore be
used as a tool in preparing atorvastatin calcium substantially free
of AED.
Inventors: |
Finkelstein; Nina;
(Herzliya, IL) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Assignee: |
Teva Pharmaceuticals USA,
Inc.
|
Family ID: |
35545174 |
Appl. No.: |
12/584311 |
Filed: |
September 2, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11236647 |
Sep 28, 2005 |
|
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12584311 |
|
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60613687 |
Sep 28, 2004 |
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Current U.S.
Class: |
73/61.55 ;
548/537 |
Current CPC
Class: |
A61P 3/06 20180101; C07D
207/34 20130101; C07D 493/04 20130101; A61P 9/10 20180101; A61P
7/02 20180101 |
Class at
Publication: |
73/61.55 ;
548/537 |
International
Class: |
G01N 30/16 20060101
G01N030/16; C07D 207/34 20060101 C07D207/34 |
Claims
1-23. (canceled)
24. A method for determining the level of atorvastatin epoxy
dihydroxy (AED) in atorvastatin calcium comprising (a) measuring by
HPLC the area under a peak corresponding to AED in a reference
standard comprising a known amount of AED; (b) measuring by HPLC
the area under a peak corresponding to AED in a sample comprising
atorvastatin calcium and AED; and (c) determining the amount of AED
in the sample by comparing the area of step (a) to the area of step
(b).
25. The method of claim 24, wherein atorvastatin calcium is either
crude atorvastatin calcium or any form of atorvastatin calcium.
26. The method of claim 25, wherein said form of atorvastatin
calcium is selected from the group consisting of form I, II, IV, V,
VI, VII, VIII, IX, X, XI, XII, and amorphous.
27. The method of claim 24, wherein the measuring by HPLC in step
(a), step (b), or both, includes the following: (i) preparing
solutions by combining the atorvastatin calcium sample of step (a),
and the reference standard of step (b), with a mixture of
acetonitrile:tetrahydrofuran:water in a ratio of about 60:5:35, to
obtain a solution; (ii) injecting the solutions prepared in step
(i) into a 250.times.4.6 mm KR 100 5C-18 (or similar) column; (iii)
eluting the standard or sample that was injected in step (ii) from
the column at about 50 min using a mixture of
acetonitrile:tetrahydrofuran:buffer (31:9:60) and
acetonitrile:buffer mix (75:25) as an eluent, and (d) measuring the
AED content in the sample with a UV detector.
28. The method of claim 27, wherein the UV wavelength is about 254
nm.
29. An HPLC method for assaying atorvastatin calcium that contains
AED comprising the steps of (a) combining an atorvastatin calcium
sample with a mixture of acetonitrile:tetrahydrofuran:water in a
ratio of about 60:5:35, to obtain a solution; (b) injecting the
solution of step (a) into a 250.times.4.6 mm KR 100 5C-18 (or
similar) column; (c) eluting the sample from the column at about 50
min using a mixture of acetonitrile:tetrahydrofuran:buffer
(31:9:60) and acetonitrile:buffer mix (75:25) as an eluent, and (d)
measuring the AED content in the sample with a UV detector by
comparing with HPLC, carried out as in steps (b) and (c), of a
reference standard comprising a known amount of AED.
30. The method of claim 29, wherein the UV wavelength is about 254
nm.
31. The method of claim 29, wherein the buffer contains an aqueous
solution of NH.sub.4H.sub.2PO.sub.4 in a concentration of about
0.05M having a pH of about 5, and ammonium hydroxide.
32. The method of claim 31, wherein the ratio of the said aqueous
solution of NH.sub.4H.sub.2PO.sub.4 and the ammonium hydroxide is
of about 1 to 4, respectively.
33. The method of claim 29, wherein the buffer mix contains a
buffer and tetrahydrofuran; wherein the buffer contains an aqueous
solution of NH.sub.4H.sub.2PO.sub.4 in a concentration of about
0.05M having a pH of about 5, and ammonium hydroxide.
34. The method of claim 33, wherein the ratio of the said buffer
and tetrahydrofuran is about 1 to 6.67, respectively.
35. A process for preparing a form of atorvastatin calcium
comprising less than about 0.10 w/w of AED, by HPLC comprising the
steps of (a) obtaining one or more samples of one or more
atorvastatin calcium batches; (b) measuring the level of AED in
each of the samples of (a); (c) selecting the atorvastatin calcium
batch that comprises a level of AED of less than a about 0.10 w/w
by HPLC, based on the measurement or measurements conducted in step
(b); and (d) using the batch selected in step (c) to prepare said
any form of atorvastatin calcium.
36. The process of claim 35, wherein the atorvastatin calcium
sample of step (a) contains less than about 0.05 w/w by HPLC of
AED.
37. The process of claim 35, wherein said any form of atorvastatin
calcium is selected from the group consisting of form I, II, IV, V,
VI, VII, VIII, IX, X, XI, XII, and amorphous.
38. The process of claim 35, wherein, if the atorvastatin calcium
sample in step (a) contains more than about 0.10 w/w by HPLC of
AED, the sample may be purified, prior to performing step (c).
39. The process of claim 35, wherein the atorvastatin calcium of
step (a) obtained after purification, contains less than about 0.10
w/w by HPLC of AED.
40. The process of claim 39, wherein the atorvastatin calcium of
step (a) obtained after purification, contains less than about 0.05
w/w by HPLC of AED.
41. The process of claim 35, wherein the purification is done by
crystallization from an organic solvent, water, or mixtures
thereof.
42-106. (canceled)
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/613,687 filed Sep. 28, 2004, which
is incorporated herein by reference.
FIELD OF INVENTION
[0002] The present invention relates to atorvastatin calcium
impurities and processes for preparing atorvastatin calcium
substantially free of impurities.
BACKGROUND OF THE INVENTION
[0003]
(.beta.R,.delta.R)-2-(4-fluorophenyl)-.beta.,.delta.-dihydroxy-5-(1-
-methylethyl)-3-phenyl-4-[(phenylamino)carbonyl]-1H-pyrrole-1-heptanoic
acid ("atorvastatin") of formula (I)
##STR00001##
is well known in the art, and described, inter alia, in U.S. Pat.
Nos. 4,681,893, 5,273,995.
[0004] Atorvastatin calcium is a member of the class of drugs
called statins. Statin drugs are said to be the most
therapeutically effective drugs currently available for reducing
low density lipoprotein (LDL) particle concentration in the blood
stream of patients at risk for cardiovascular disease. A high level
of LDL in the bloodstream has been linked to the formation of
coronary lesions which obstruct the flow of blood and can rupture
and promote thrombosis. Goodman and Gilman's The Pharmacological
Basis of Therapeutics 879 (9.sup.th ed. 1996). Reducing plasma LDL
levels has been shown to reduce the risk of clinical events in
patients with cardiovascular disease and patients who are free of
cardiovascular disease but who have hypercholesterolemia.
Scandinavian Simvastatin Survival Study Group, 1994; Lipid Research
Clinics Program, 1984a, 1984b.
[0005] Atorvastatin calcium is marketed under the name LIPITOR.RTM.
by Pfizer, Inc. Atorvastatin was first claimed in U.S. Pat. No.
4,681,893. The hemi-calcium salt of atorvastatin is disclosed in
U.S. Pat. No. 5,273,995. Distinct crystalline forms are disclosed
in several patents and patent applications. Crystalline Forms I,
II, III and IV of atorvastatin calcium are the subjects of U.S.
Pat. Nos. 5,959,156 and 6,121,461 assigned to Warner-Lambert and
crystalline atorvastatin calcium Forms V and VIII are disclosed in
commonly-owned published application nos. WO 01/36384 and US
2002/0183378, both of which are herein incorporated by
reference.
[0006] Like any synthetic compound, atorvastatin hemi-calcium salts
can contain extraneous compounds or impurities that can come from
many sources. They can be unreacted starting materials, by-products
of the reaction, products of side reactions, or degradation
products. Impurities in atorvastatin hemi-calcium salts or any
active pharmaceutical ingredient (API) are undesirable and, in
extreme cases, might even be harmful to a patient being treated
with a dosage form containing the API.
[0007] It is also known in the art that impurities in an API may
arise from degradation of the API itself, which is related to the
stability of the pure API during storage, and the manufacturing
process, including the chemical synthesis. Process impurities
include unreacted starting materials, chemical derivatives of
impurities contained in starting materials, synthetic by-products,
and degradation products.
[0008] In addition to stability, which is a factor in the shelf
life of the API, the purity of the API produced in the commercial
manufacturing process is clearly a necessary condition for
commercialization. Impurities introduced during commercial
manufacturing processes must be limited to very small amounts, and
are preferably substantially absent. For example, the ICH Q7A
guidance for API manufacturers requires that process impurities be
maintained below set limits by specifying the quality of raw
materials, controlling process parameters, such as temperature,
pressure, time, and stoichiometric ratios, and including
purification steps, such as crystallization, distillation, and
liquid-liquid extraction, in the manufacturing process.
[0009] The product mixture of a chemical reaction is rarely a
single compound with sufficient purity to comply with
pharmaceutical standards. Side products and by-products of the
reaction and adjunct reagents used in the reaction will, in most
cases, also be present in the product mixture. At certain stages
during processing of an API, such as atorvastatin calcium, it must
be analyzed for purity, typically, by HPLC or TLC analysis, to
determine if it is suitable for continued processing and,
ultimately, for use in a pharmaceutical product. The API need not
be absolutely pure, as absolute purity is a theoretical ideal that
is typically unattainable. Rather, purity standards are set with
the intention of ensuring that an API is as free of impurities as
possible, and, thus, is as safe as possible for clinical use. As
discussed above, in the United States, the Food and Drug
Administration guidelines recommend that the amounts of some
impurities be limited to less than 0.1 percent.
[0010] Generally, side products, by-products, and adjunct reagents
(collectively "impurities") are identified spectroscopically and/or
with another physical method, and then associated with a peak
position, such as that in a chromatogram, or a spot on a TLC plate.
(Strobel p. 953, Strobel, H. A.; Heineman, W. R., Chemical
Instrumentation: A Systematic Approach, 3rd dd. (Wiley & Sons:
New York 1989)). Thereafter, the impurity can be identified, e.g.,
by its relative position in the chromatogram, where the position in
a chromatogram is conventionally measured in minutes between
injection of the sample on the column and elution of the particular
component through the detector. The relative position in the
chromatogram is known as the "retention time."
[0011] The retention time can vary about a mean value based upon
the condition of the instrumentation, as well as many other
factors. To mitigate the effects such variations have upon accurate
identification of an impurity, practitioners use the "relative
retention time" ("RRT") to identify impurities. (Strobel p. 922).
The RRT of an impurity is its retention time divided by the
retention time of a reference marker. It may be advantageous to
select a compound other than the API that is added to, or present
in, the mixture in an amount sufficiently large to be detectable
and sufficiently low as not to saturate the column, and to use that
compound as the reference marker for determination of the RRT.
[0012] Those skilled in the art of drug manufacturing research and
development understand that a compound in a relatively pure state
can be used as a "reference standard." A reference standard is
similar to a reference marker, which is used for qualitative
analysis only, but is used to quantify the amount of the compound
of the reference standard in an unknown mixture, as well. A
reference standard is an "external standard," when a solution of a
known concentration of the reference standard and an unknown
mixture are analyzed using the same technique. (Strobel p. 924,
Snyder p. 549, Snyder, L. R.; Kirkland, J. J. Introduction to
Modern Liquid Chromatography, 2nd ed. (John Wiley & Sons: New
York 1979)). The amount of the compound in the mixture can be
determined by comparing the magnitude of the detector response. See
also U.S. Pat. No. 6,333,198, incorporated herein by reference.
[0013] The reference standard can also be used to quantify the
amount of another compound in the mixture if a "response factor,"
which compensates for differences in the sensitivity of the
detector to the two compounds, has been predetermined. (Strobel p.
894). For this purpose, the reference standard is added directly to
the mixture, and is known as an "internal standard." (Strobel p.
925, Snyder p. 552).
[0014] The reference standard can serve as an internal standard
when, without the deliberate addition of the reference standard, an
unknown mixture contains a detectable amount of the reference
standard compound using the technique known as "standard
addition."
[0015] In a the "standard addition technique", at least two samples
are prepared by adding known and differing amounts of the internal
standard. (Strobel pp. 391-393, Snyder pp. 571, 572). The
proportion of the detector response due to the reference standard
present in the mixture without the addition can be determined by
plotting the detector response against the amount of the reference
standard added to each of the samples, and extrapolating the plot
to zero concentration of the reference standard. (See, e.g.,
Strobel, FIG. 11.4 p. 392). The response of a detector in HPLC
(e.g. UV detectors or refractive index detectors) can be and
typically is different for each compound eluting from the HPLC
column. Response factors, as known, account for this difference in
the response signal of the detector to different compounds eluting
from the column.
[0016] As is known by those skilled in the art, the management of
process impurities is greatly enhanced by understanding their
chemical structures and synthetic pathways, and by identifying the
parameters that influence the amount of impurities in the final
product.
[0017] Like any synthetic compound, atorvastatin calcium can
contain extraneous compounds or impurities that can come from many
sources. They can be unreacted starting materials, by-products of
the reaction, products of side reactions, or degradation
products.
[0018] In this application the reference marker is the impurity
N-formyl atorvastatin calcium in the API. Detection or
quantification of the reference marker serves to establish the
level of purity of the API. Use of a compound as a reference marker
requires recourse to a sample of substantially pure compound.
[0019] Thus, there is a need in the art for a method for
determining the level of impurities in atorvastatin calcium
samples.
SUMMARY OF THE INVENTION
[0020] In one aspect the present invention provides the isolated
atorvastatin calcium derivative--atorvastatin calcium epoxy
dihydroxy (AED), having the formula:
##STR00002##
The isolated AED of the present invention may be characterized by
data selected from: .sup.1HNMR spectrum having hydrogen chemical
shifts at about 1.20, 1.21, 2.37, 4.310, 6.032, 7.00, 7.06-7.29,
7.30, 7.39, 7.41, 7.56 ppm; a .sup.13CNMR spectrum having carbon
chemical shifts at about 16.97, 34.66, 103.49, 106.66, 114.72,
120.59, 125.79, 128.21, 128.55, 128.74, 129.06, 129.57, 132.38,
132.51, 135.15, 161.61, 163.23 ppm; an MS (ESI.sup.+) spectrum
having peaks at about having: m/z=472(MNa).sup.+, 454
(MNa--H.sub.2O).sup.+, 432 (MH--H.sub.2O).sup.+; 344
(FPhCOC(Ph)=C--CONHPh).sup.+ by retention time of about 32 min in
HPLC analysis, such as the one described herein below, and by a
relative retention time of about 1.88.
[0021] In another aspect, the present invention further provides a
process for preparing AED comprising the steps of: [0022] (a)
combining atorvastatin calcium salt and a polar organic solvent or
mixtures thereof with water, with methylene blue, to obtain a
solution; [0023] (b) irradiating the obtained solution for about 2
to about 10 hours; [0024] (c) recovering AED.
[0025] Preferably, the irradiation of the solution of step (a) is
performed in the presence of oxygen or air, in order to produce a
photooxidation reaction. Therefore, the reaction is conducted,
preferably, in an open vessel.
[0026] Preferably, the light source for irradiation is selected
from the group consisting of a tungsten lamp, a UV lamp or sun
light. More preferably, the light source for irradiation is a
tungsten lamp. Moreover, when using a tungsten lamp as a light
source, the yield is increased.
[0027] In yet another aspect, the present invention also provides a
method for determining the level of AED in atorvastatin calcium
comprising [0028] (a) measuring by HPLC the area under a peak
corresponding to AED in a reference standard comprising a known
amount of AED; [0029] (b) measuring by HPLC the area under a peak
corresponding to AED in a sample comprising atorvastatin calcium
and AED; [0030] (c) determining the amount of AED in the sample by
comparing the area of step (a) to the area of step (b).
[0031] Unless otherwise specified, "atorvastatin calcium" may be
either crude atorvastatin calcium or any form of atorvastatin,
including, for example, crystalline Forms I, II, IV, V, VI, VII,
VIII, IX, X, XI, XII and amorphous.
[0032] Preferably, the HPLC methodology used in the above method
(for the use of AED as reference standard) includes the steps
[0033] (a) combining an atorvastatin calcium sample with a mixture
of acetonitrile:tetrahydrofuran:water in a ratio of about 60:5:35,
to obtain a solution; [0034] (b) injecting the solution of step (a)
into a 250.times.4.6 mm KR 100 5C-18 (or similar) column; [0035]
(c) eluting the sample from the column at about 50 min using a
mixture of acetonitrile:tetrahydrofuran:buffer (31:9:60) and
acetonitrile:buffer mix (75:25) as an eluent, and [0036] (d)
measuring the AED content in the relevant sample with a UV detector
(preferably at a 254 nm wavelength).
[0037] In one aspect, the present invention provides an HPLC method
for assaying atorvastatin calcium comprising the steps [0038] (a)
combining an atorvastatin calcium sample with a mixture of
acetonitrile:tetrahydrofuran:water in a ratio of about 60:5:35, to
obtain a solution; [0039] (b) injecting the solution of step (a)
into a 250.times.4.6 mm KR 100 5C-18 (or similar) column; [0040]
(c) eluting the sample from the column at about 50 min using a
mixture of acetonitrile:tetrahydrofuran:buffer (31:9:60) and
acetonitrile:buffer mix (75:25) as an eluent, and [0041] (d)
measuring the AED content in the relevant sample with a UV detector
(preferably at a 254 nm wavelength).
[0042] Preferably, the buffer contains an aqueous solution of
NH.sub.4H.sub.2PO.sub.4 in a concentration of about 0.05M having a
pH of about 5, and ammonium hydroxide. Preferably, the ratio of the
aqueous solution of NH.sub.4H.sub.2PO.sub.4 and ammonium hydroxide
is of about 1 to 4, respectively.
[0043] Preferably, the buffer mix contains the above buffer and
tetrahydrofuran. Preferably, the ratio of the above buffer and
tetrahydrofuran is of about 1 to 6.67, respectively.
[0044] In another aspect, the present invention provides a process
for preparing a form of atorvastatin calcium comprising less than
about 0.10 w/w of, AED, by HPLC comprising the steps of [0045] (a)
obtaining one or more samples of one or more atorvastatin calcium
batches; [0046] (b) measuring the level of AED in each of the
samples of (a); [0047] (c) selecting the atorvastatin calcium batch
that comprises a level of AED of less than about 0.10 w/w by HPLC,
based on the measurement or measurements conducted in step (b); and
[0048] (d) using the batch selected in step (c) to prepare said any
form of atorvastatin calcium.
[0049] Preferably, the atorvastatin calcium sample of step (a)
comprises a sufficiently low level of AED. More preferably, the
atorvastatin calcium sample of step (a) contains less than about
0.05 w/w by HPLC of AED.
[0050] Preferably, said any form of atorvastatin calcium refers to
but is not limited to forms I, II, IV, V, VI, VII, VIII, IX, X, XI,
XII and amorphous.
[0051] When the atorvastatin calcium sample of step (a) contains
more than about 0.10 w/w by HPLC of AED, according to the
measurement in step (b), the sample may be purified, prior to
performing step (c).
[0052] Preferably, the atorvastatin calcium sample of step (a)
obtained after purification, contains less than about 0.10 w/w by
HPLC of AED, more preferably, of less than about 0.05 w/w by
HPLC.
[0053] In yet another aspect, the present invention provides a
method for reducing the level of AED in atorvastatin calcium sample
by dissolving a selected form of atorvastatin calcium in an organic
solvent, water or mixtures thereof, and crystallizing to obtain
atorvastatin calcium having a reduced level of AED.
[0054] Preferably, the atorvastatin calcium sample obtained after
purification contains less than about 0.10 w/w by HPLC of AED, more
preferably, of less than about 0.05 w/w by HPLC.
[0055] Preferably, the selected form of atorvastatin calcium may be
any form of atorvastatin, such as but not limited to form I, II,
IV, V, VI, VII, VIII, IX, X, XI, XII and amorphous.
[0056] Preferably, when the selected form of atorvastatin calcium
is the amorphous form, the crystallization is performed from either
a mixture of ester and C.sub.5-10 cyclic or aliphatic hydrocarbon,
from a polar aprotic organic solvent or from a mixture of a
C.sub.6-10 aromatic hydrocarbon and a polar organic solvent, to
give atorvastatin calcium amorphous form. Preferably, the ester is
ethylacetate. A preferred C.sub.5-10 cyclic or aliphatic
hydrocarbon is hexane. Preferably, the polar organic solvent is
either a ketone or a nitrile. A preferred ketone is acetone. A
preferred nitrile is acetonitrile. Preferably, the C.sub.6-10
aromatic hydrocarbon is toluene. A preferred polar organic solvent
is tetrahydrofuran.
[0057] Preferably, when the selected form of atorvastatin calcium
is form I, the crystallization is performed from a mixture of water
miscible organic solvent and water, to give atorvastatin calcium
form I. Preferably, the polar organic solvent is a mixture of
C.sub.1-4 alcohol and an ether. Preferably, the C.sub.1-4 alcohol
is methanol. A preferred ether is methyltertbutylether.
[0058] Preferably, when the selected form of atorvastatin calcium
is form II, the crystallization is performed from a mixture of
water miscible organic solvent and water, to give atorvastatin
calcium form II. Preferably, the water miscible organic solvent is
a C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is
methanol.
[0059] Preferably, when the selected form of atorvastatin calcium
is form IV, the crystallization is performed from a water miscible
organic solvent, water and mixtures thereof, to give atorvastatin
calcium form IV. Preferably, the water miscible organic solvent is
a C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is methanol,
ethanol or 1-butanol. Preferably, when a mixture of a water
miscible organic solvent and water is used, the water miscible
organic solvent is ethanol.
[0060] Preferably, when the selected form of atorvastatin calcium
is form V, the crystallization is performed from a mixture of water
miscible organic solvent and water, to give atorvastatin calcium
form V. Preferably, the water miscible organic solvent is a
C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is
ethanol.
[0061] Preferably, when the selected form of atorvastatin calcium
is form VI, the crystallization is performed from a mixture of
polar aprotic organic solvent and water, to give atorvastatin
calcium form VI. Preferably, the polar aprotic organic solvent is a
ketone. Preferably, the ketone is acetone.
[0062] Preferably, when the selected form of atorvastatin calcium
is form VII, the crystallization is performed from a C.sub.1-4
alcohol, to give atorvastatin calcium form VII. Preferably, the
C.sub.1-4 alcohol is ethanol.
[0063] Preferably, when the selected form of atorvastatin calcium
is form VIII, the crystallization is performed from a water
miscible organic solvent, water and mixtures thereof, to give
atorvastatin calcium form VIII. Preferably, the water miscible
organic solvent is a C.sub.1-4 alcohol. Preferably, the C.sub.1-4
alcohol is ethanol, methanol, 1-butanol or iso-propanol.
[0064] Preferably, when the selected form of atorvastatin calcium
is form IX, the crystallization is performed from a water miscible
organic solvent, a C.sub.5-10 aliphatic hydrocarbon, water and
mixtures thereof, to give atorvastatin calcium form IX. Preferably,
the water miscible organic solvent is a C.sub.1-4 alcohol.
Preferably, the C.sub.1-4 alcohol is ethanol, 1-butanol or
iso-propanol. Preferably, the C.sub.5-10 aliphatic hydrocarbon is
hexane.
[0065] Preferably, when the selected form of atorvastatin calcium
is form X, the crystallization is performed from a mixture of a
water miscible organic solvent and water, to give atorvastatin
calcium form X. Preferably, the water miscible organic solvent is a
C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is
ethanol.
[0066] Preferably, when the selected form of atorvastatin calcium
is form XI, the crystallization is performed from a polar aprotic
organic solvent or from a water miscible organic solvent, to give
atorvastatin calcium form XI. Preferably, the polar aprotic organic
solvent is a ketone. Preferably, the water miscible organic solvent
is a C.sub.1-4 alcohol. Preferably, the ketone is
methylethylketone. A preferred C.sub.1-4 alcohol is
isopropanol.
[0067] Preferably, when the selected form of atorvastatin calcium
is form XII, the crystallization is performed from a mixture of a
water miscible organic solvent and water, to give atorvastatin
calcium form XII. Preferably, the water miscible organic solvent is
a C.sub.1-4 alcohol. A preferred C.sub.1-4 alcohol is ethanol.
BRIEF DESCRIPTION OF THE DRAWINGS
[0068] FIG. 1: HPLC chromatogram of AED.
[0069] FIG. 2: .sup.1HNMR spectrum of AED.
[0070] FIG. 3: .sup.13CNMR spectrum of AED.
[0071] FIG. 4: MS spectrum of AED.
DETAILED DESCRIPTION OF THE INVENTION
[0072] The present invention provides the isolated atorvastatin
calcium derivative--atorvastatin calcium epoxy dihydroxy (AED),
having the formula:
##STR00003##
The isolated AED of the present invention may be characterized by
data selected from: .sup.1HNMR spectrum having hydrogen chemical
shifts at about 1.20, 1.21, 2.37, 4.310, 6.032, 7.00, 7.06-7.29,
7.30, 7.39, 7.41, 7.56 ppm; a .sup.13CNMR spectrum having carbon
chemical shifts at about 16.97, 34.66, 103.49, 106.66, 114.72,
120.59, 125.79, 128.21, 128.55, 128.74, 129.06, 129.57, 132.38,
132.51, 135.15, 161.61, 163.23 ppm an MS (ESI.sup.+) spectrum
having peaks at about having: m/z=472(MNa).sup.+, 454
(MNa--H.sub.2O).sup.+, 432 (MH--H.sub.2O).sup.+; 344
(FPhCOC(Ph)=C--CONHPh).sup.+ by retention time of about 32 min in
HPLC analysis, such as the one described herein below, and by a
relative retention time of about 1.88.
[0073] The present invention further provides a process for
preparing AED comprising the steps of: [0074] (a) combining
atorvastatin calcium salt and a polar organic solvent or mixtures
thereof with water, with methylene blue, to obtain a solution;
[0075] (b) irradiating the obtained solution for about 2 to about
10 hours; [0076] (c) recovering AED.
[0077] Preferably, the polar organic solvent is selected from the
group consisting of C.sub.1-4 alcohol and nitrile. Preferably, the
C.sub.1-4 alcohol is either methanol or ethanol. A preferred
nitrile is acetonitrile. Preferably, a mixture of acetonitrile and
water is used in step (a).
[0078] Preferably, the irradiation of the solution of step (a) is
performed in the presence of oxygen or air, in order to produce a
photooxidation reaction. Therefore, the reaction is conducted,
preferably, in an open vessel.
[0079] Preferably, the light source for irradiation is selected
from the group consisting of a tungsten lamp, a UV lamp or sun
light. More preferably, the light source for irradiation is a
tungsten lamp. Moreover, when using a tungsten lamp as a light
source, the yield is increased.
[0080] Preferably, the solution of step (a) is irradiated for about
2 hours.
[0081] Preferably, the crude AED may recovered by evaporating the
polar organic solvent or mixtures thereof with water, more
preferably, under vacuum, followed by filtration and drying to
obtain a precipitate, crude AED.
[0082] The recovered crude AED may be purified by a process of
chromatography on a silica-gel column with an eluent of water
immiscible polar organic solvent or a mixture of a polar organic
solvent and a C.sub.5-8 aliphatic hydrocarbon. Preferably, the
water immiscible polar organic solvent is dichloromethane. A
preferred polar organic solvent is ethyl acetate.
[0083] Preferably, AED may be further purified by a process of
precipitation from a water immiscible polar organic solvent or from
a mixture of a polar organic solvent and a C.sub.5-10 aliphatic
hydrocarbon. Preferably, the water immiscible polar organic solvent
is dichloromethane. A preferred polar organic solvent is ethyl
acetate. Preferably, the C.sub.5-10 aliphatic hydrocarbon is
hexane.
[0084] The present invention also provides a method for determining
the level of AED in atorvastatin calcium comprising [0085] (a)
measuring by HPLC the area under a peak corresponding to AED in a
reference standard comprising a known amount of AED; [0086] (b)
measuring by HPLC the area under a peak corresponding to AED in a
sample comprising atorvastatin calcium and AED; [0087] (c)
determining the amount of AED in the sample by comparing the area
of step (a) to the area of step (b).
[0088] Unless otherwise specified, "atorvastatin calcium" may be
either crude atorvastatin calcium or any form of atorvastatin,
including, for example, crystalline Forms I, II, IV, V, VI, VII,
VIII, IX, X, XI, XII and amorphous.
[0089] Preferably, the HPLC methodology used in the above method
(for the use of AED as reference standard) includes the steps
[0090] (a) combining an atorvastatin calcium sample with a mixture
of acetonitrile:tetrahydrofuran:water in a ratio of about 60:5:35,
to obtain a solution; [0091] (b) injecting the solution of step (a)
into a 250.times.4.6 mm KR 100 5C-18 (or similar) column; [0092]
(c) eluting the sample from the column at about 50 min using a
mixture of acetonitrile:tetrahydrofuran:buffer (31:9:60) and
acetonitrile:buffer mix (75:25) as an eluent, and [0093] (d)
measuring the AED content in the relevant sample with a UV detector
(preferably at a 254 nm wavelength).
[0094] The present invention further provides an HPLC method for
assaying atorvastatin calcium comprising the steps [0095] (a)
combining an atorvastatin calcium sample with a mixture of
acetonitrile:tetrahydrofuran:water in a ratio of about 60:5:35, to
obtain a solution; [0096] (b) injecting the solution of step (a)
into a 250.times.4.6 mm KR 100 5C-18 (or similar) column; [0097]
(c) eluting the sample from the column at about 50 min using a
mixture of acetonitrile:tetrahydrofuran:buffer (31:9:60) and
acetonitrile:buffer mix (75:25) as an eluent, and [0098] (d)
measuring the AED content in the relevant sample with a UV detector
(preferably at a 254 nm wavelength).
[0099] Preferably, the buffer contains an aqueous solution of
NH.sub.4H.sub.2PO.sub.4 in a concentration of about 0.05M having a
pH of about 5, and ammonium hydroxide. Preferably, the ratio of the
aqueous solution of NH.sub.4H.sub.2PO.sub.4 and ammonium hydroxide
is of about 1 to 4, respectively.
[0100] Preferably, the buffer mix contains the above buffer and
tetrahydrofuran. Preferably, the ratio of the above buffer and
tetrahydrofuran is of about 1 to 6.67, respectively.
[0101] The present invention provides a process for preparing a
form of atorvastatin calcium comprising less than about 0.10 w/w
of, AED, by HPLC comprising the steps of [0102] (a) obtaining one
or more samples of one or more atorvastatin calcium batches; [0103]
(b) measuring the level of AED in each of the samples of (a);
[0104] (c) selecting the atorvastatin calcium batch that comprises
a level of AED of less than about 0.10 w/w by HPLC, based on the
measurement or measurements conducted in step (b); and [0105] (d)
using the batch selected in step (c) to prepare said any form of
atorvastatin calcium.
[0106] Preferably, the atorvastatin calcium sample of step (a)
comprises a sufficiently low level of AED. More preferably, the
atorvastatin calcium sample of step (a) contains less than about
0.05 w/w by HPLC of AED.
[0107] Preferably, said any form of atorvastatin calcium refers to
but is not limited to forms I, II, IV, V, VI, VII, VIII, IX, X, XI,
XII and amorphous.
[0108] When the atorvastatin calcium sample of step (a) contains
more than about 0.10 w/w by HPLC of AED, according to the
measurement in step (b), the sample may be purified, prior to
performing step (c).
[0109] Preferably, the atorvastatin calcium sample of step (a)
obtained after purification, contains less than about 0.10 w/w by
HPLC of AED, more preferably, of less than about 0.05 w/w by
HPLC.
[0110] The purification may be performed by crystallization from an
organic solvent, water, or mixtures thereof.
[0111] The present invention also provides a method for reducing
the level of AED in atorvastatin calcium sample by dissolving a
selected form of atorvastatin calcium in an organic solvent, water
or mixtures thereof, and crystallizing to obtain atorvastatin
calcium having a reduced level of AED.
[0112] Preferably, the atorvastatin calcium sample obtained after
purification contains less than about 0.10 w/w by HPLC of AED, more
preferably, of less than about 0.05 w/w by HPLC.
[0113] Preferably, the selected form of atorvastatin calcium may be
any form of atorvastatin, such as but not limited to form I, II,
IV, V, VI, VII, VIII, IX, X, XI, XII and amorphous.
[0114] Preferably, when the selected form of atorvastatin calcium
is the amorphous form, the crystallization is performed from either
a mixture of ester and C.sub.5-10 cyclic or aliphatic hydrocarbon,
from a polar aprotic organic solvent or from a mixture of a
C.sub.6-10 aromatic hydrocarbon and a polar organic solvent, to
give atorvastatin calcium amorphous form. Preferably, the ester is
ethylacetate. A preferred C.sub.5-10 cyclic or aliphatic
hydrocarbon is hexane. Preferably, the polar organic solvent is
either a ketone or a nitrile. A preferred ketone is acetone. A
preferred nitrile is acetonitrile. Preferably, the C.sub.6-10
aromatic hydrocarbon is toluene. A preferred polar organic solvent
is tetrahydrofuran.
[0115] Preferably, when the selected form of atorvastatin calcium
is form I, the crystallization is performed from a mixture of water
miscible organic solvent and water, to give atorvastatin calcium
form I. Preferably, the polar organic solvent is a mixture of
C.sub.1-4 alcohol and an ether. Preferably, the C.sub.1-4 alcohol
is methanol. A preferred ether is methyltertbutylether.
[0116] Preferably, when the selected form of atorvastatin calcium
is form II, the crystallization is performed from a mixture of
water miscible organic solvent and water, to give atorvastatin
calcium form II. Preferably, the water miscible organic solvent is
a C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is
methanol.
[0117] Preferably, when the selected form of atorvastatin calcium
is form IV, the crystallization is performed from a water miscible
organic solvent, water and mixtures thereof, to give atorvastatin
calcium form IV. Preferably, the water miscible organic solvent is
a C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is methanol,
ethanol or 1-butanol. Preferably, when a mixture of a water
miscible organic solvent and water is used, the water miscible
organic solvent is ethanol.
[0118] Preferably, when the selected form of atorvastatin calcium
is form V, the crystallization is performed from a mixture of water
miscible organic solvent and water, to give atorvastatin calcium
form V. Preferably, the water miscible organic solvent is a
C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is
ethanol.
[0119] Preferably, when the selected form of atorvastatin calcium
is form VI, the crystallization is performed from a mixture of
polar aprotic organic solvent and water, to give atorvastatin
calcium form VI. Preferably, the polar aprotic organic solvent is a
ketone. Preferably, the ketone is acetone.
[0120] Preferably, when the selected form of atorvastatin calcium
is form VII, the crystallization is performed from a C.sub.1-4
alcohol, to give atorvastatin calcium form VII. Preferably, the
C.sub.1-4 alcohol is ethanol.
[0121] Preferably, when the selected form of atorvastatin calcium
is form VIII, the crystallization is performed from a water
miscible organic solvent, water and mixtures thereof, to give
atorvastatin calcium form VIII. Preferably, the water miscible
organic solvent is a C.sub.1-4 alcohol. Preferably, the C.sub.1-4
alcohol is ethanol, methanol, 1-butanol or iso-propanol.
[0122] Preferably, when the selected form of atorvastatin calcium
is form IX, the crystallization is performed from a water miscible
organic solvent, a C.sub.5-10 aliphatic hydrocarbon, water and
mixtures thereof, to give atorvastatin calcium form IX. Preferably,
the water miscible organic solvent is a C.sub.1-4 alcohol.
Preferably, the C.sub.1-4 alcohol is ethanol, 1-butanol or
iso-propanol. Preferably, the C.sub.5-10 aliphatic hydrocarbon is
hexane.
[0123] Preferably, when the selected form of atorvastatin calcium
is form X, the crystallization is performed from a mixture of a
water miscible organic solvent and water, to give atorvastatin
calcium form X. Preferably, the water miscible organic solvent is a
C.sub.1-4 alcohol. Preferably, the C.sub.1-4 alcohol is
ethanol.
[0124] Preferably, when the selected form of atorvastatin calcium
is form XI, the crystallization is performed from a polar aprotic
organic solvent or from a water miscible organic solvent, to give
atorvastatin calcium form XI. Preferably, the polar aprotic organic
solvent is a ketone. Preferably, the water miscible organic solvent
is a C.sub.1-4 alcohol. Preferably, the ketone is
methylethylketone. A preferred C.sub.1-4 alcohol is
isopropanol.
[0125] Preferably, when the selected form of atorvastatin calcium
is form XII, the crystallization is performed from a mixture of a
water miscible organic solvent and water, to give atorvastatin
calcium form XII. Preferably, the water miscible organic solvent is
a C.sub.1-4 alcohol. A preferred C.sub.1-4 alcohol is ethanol.
[0126] Optionally, the crystallization process may be repeated as
necessary to obtain the desired atorvastatin calcium purity.
[0127] In order to preserve the purity level of atorvastatin
calcium, the sample is maintained at a temperature of less than
about 8.degree. C., preferably the sample is maintained at a
temperature of less than about 4.degree. C.
[0128] Having described the invention with reference to certain
preferred embodiments, other embodiments will become apparent to
one skilled in the art from consideration of the specification. The
invention is further defined by reference to the following examples
describing in detail the preparation of the composition and methods
of use of the invention. It will be apparent to those skilled in
the art that many modifications, both to materials and methods, may
be practiced without departing from the scope of the invention.
EXAMPLES
General
[0129] NMR analysis was done on Bruker DPX (300 MHz for .sup.1HNMR,
150 MHz for .sup.13CNMR), solvent CDCl.sub.3.
[0130] Mass spectrometry was done on Micromass Q-TOS by method
ESI.sup.+
HPLC Method
[0131] Column & Packing: Kromasil KR 100 5C-18 250.times.4.6 mm
is suitable. [0132] Eluent A: Acetonitrile:Tetrahydrofuran:Buffer
31:9:60 [0133] Eluent B: Acetonitrile:Buffer Mix 75:25 [0134]
Buffer solution: 0.05M aqueous NH.sub.4H.sub.2PO.sub.4 adjusted to
pH 5.0 with NH.sub.4OH (diluted about 1:4) [0135] Buffer Mix: A
mixture of buffer solution and THF 60 volumes buffer and 9 volumes
THF [0136] Gradient conditions:
TABLE-US-00001 [0136] Time (minutes) % Eluent A % Eluent B Flow
rate 0 100 0 1.8 20 100 0 1.8 30 45 55 2.0 40 0 100 2.5 50 0 100
2.5
[0137] Detector: 254 nm [0138] Diluent: 60:5:35
Acetonitrile:Tetrahydrofuran:water
Example 1
Atorvastatin Epoxy Dihydroxy Synthesis
[0139] Atorvastatin calcium salt (1.0 g) was dissolved in a mixture
of acetonitrile-water (1200 ml-800 ml) and methylene blue (1 mg)
was added to the solution. The solution was stirred in an open
flask at ambient temperature, and irradiated with visible light
(tungsten lamp, 100 W, distance 10 cm) for 2 hours. Acetonitrile
was evaporated under vacuum, and precipitated solid was filtered
giving, after drying, a crude product (0.5 g) containing impurities
at 32 and 33 min. (HPLC control)
[0140] The crude product (3.6 g) was purified by column
chromatography on silica gel with dichloromethane as eluent, giving
the mixture of the impurities at 32 and 33 min (1.6 g). The product
was dissolved in dichloromethane (15 ml). The solution was stirred
at ambient temperature while a solid was precipitated within a few
minutes. The solid was filtered giving, after drying, the product
(80 mg).
Example 2
Crystallization of Form VIII
[0141] Atorvastatin hemi-calcium salt form V (5 g) was added to a
boiling solution of ethanol 96% (150 ml) to obtain a solution. The
solution was refluxed for 2 hours (during that time atorvastatin
hemi-calcium salt was recrystallized), then cooled to 20.degree. C.
during 1.5 hours and stirred at this temperature for an additional
16 hours. Filtration and drying in a vacuum oven at 40.degree. C.
for 24 hours and then at 60.degree. C. for 24 hours gave
atorvastatin hemi-calcium salt form VIII.
Example 3
Crystallization of the Forms of Atorvastatin Calcium
[0142] Modifying the process in Example 2 by changing the medium of
crystallization results in the following crystal forms:
TABLE-US-00002 Crystal form Medium of crystallization Amorphous
Ethyl acetate/n-Hexane (Esters/aliphatic or cyclic or branched
Hydrocarbons) Amorphous Acetone Acetonitrile Amorphous THF/Toluene
Form I traces of MTBE/MeOH/water Form II MeOH/water Form IV
1-Butanol EtOH/water MeOH Form V EtOH/water Form VI Acetone/water
Form VII EtOH Form VIII EtOH, MeOH/water EtOH 1-Butanol/water
IPA/water Form IX 1-Butanol 1-Butanol/n-Hexane 1-Butanol/IPA
1-Butanol/water EtOH 1-Butanol/EtOH Form X EtOH/water Form XI MEK
IPA Form XII EtOH/water
* * * * *