CA2485433C - Preparation of non-crystalline and crystalline dihydrate forms of azithromycin - Google Patents
Preparation of non-crystalline and crystalline dihydrate forms of azithromycin Download PDFInfo
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Abstract
The present invention describes new procedures for the preparation of the macrolide azithromycin in its non-crystalline and crystalline dihydrate forms, which are characterized and clearly differentiated by means of the following methods and techniques:
1. IR Spectroscopy.
2. Differential Scan Calorimetry (DSC).
3. X-Ray Diffraction.
4. Hygroscopicity.
5. Crystallinity test (Light Polarized Microscopy)
1. IR Spectroscopy.
2. Differential Scan Calorimetry (DSC).
3. X-Ray Diffraction.
4. Hygroscopicity.
5. Crystallinity test (Light Polarized Microscopy)
Description
1 r Preparation of non-crystalline and crystalline dihydrate forms of azithromycin BACKGROUND OF THE INVENTION
1. Field of the Invention.
Azithromycin is the USAN generic name of the azalide 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A, which systematic name is 1-oxa-6-azacyclopentadecan-15-one,13-((2,6-dideoxy-3-C-methyl-1-3-0-methyl-alpha-L-ribo-hexopyranosyl)-oxy)-ethyl-3,4,10-trihydroxy-3,5,6,8,10,12,14-heptamethyl-11-((3,4,6-trideoxy-3-(dimethyl-amino)-beta-D-xylo-hexopyranosyl)oxy). It is a semisynthetic macrolide that shows an excellent antimicrobial activity against gram-positive and some cases of gram-negative bacteria (H.A. Kirst, G.D. Sides, Antimicrob. Agents. Chemother. 1989, 33, 1419-1422).
Clinical use of this macrolide is broadening its application to the treatment of opportunistic infections (F. Lecomte, Rev. Med. Interne 1998, 19(4), 255-61;
S.
Alvarez-Elcoro, Mayo Clin. Proc. 1999, 74(6), 613-34; J. Schater, Lancet, 1999, 354(9179), 630-35).
2. Description of the Prior Art.
Figure 1 shows the different synthetic routes to azithromycin 1. The names of the intermediates displayed in Figure 1 are gathered in the following table.
Intermediate Name 1 Azithromycin 2 Erythromycin A oxime 3 6,9-iminoether 4 9,11 -iminoether 5 Azaerythromycin A
1. Field of the Invention.
Azithromycin is the USAN generic name of the azalide 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A, which systematic name is 1-oxa-6-azacyclopentadecan-15-one,13-((2,6-dideoxy-3-C-methyl-1-3-0-methyl-alpha-L-ribo-hexopyranosyl)-oxy)-ethyl-3,4,10-trihydroxy-3,5,6,8,10,12,14-heptamethyl-11-((3,4,6-trideoxy-3-(dimethyl-amino)-beta-D-xylo-hexopyranosyl)oxy). It is a semisynthetic macrolide that shows an excellent antimicrobial activity against gram-positive and some cases of gram-negative bacteria (H.A. Kirst, G.D. Sides, Antimicrob. Agents. Chemother. 1989, 33, 1419-1422).
Clinical use of this macrolide is broadening its application to the treatment of opportunistic infections (F. Lecomte, Rev. Med. Interne 1998, 19(4), 255-61;
S.
Alvarez-Elcoro, Mayo Clin. Proc. 1999, 74(6), 613-34; J. Schater, Lancet, 1999, 354(9179), 630-35).
2. Description of the Prior Art.
Figure 1 shows the different synthetic routes to azithromycin 1. The names of the intermediates displayed in Figure 1 are gathered in the following table.
Intermediate Name 1 Azithromycin 2 Erythromycin A oxime 3 6,9-iminoether 4 9,11 -iminoether 5 Azaerythromycin A
6 Azaerythromycin 11,12-hydrogenorthoborate 7 Azitliromycin 11,12-hydrogenorthoborate The following table summarizes the patents, articles, authors and applicants that describe the different synthetic paths (A, B, C, D, E) towards azithromycin 1.
Route Patents Articles Author Applicant A a) US 4,328,334 = J. Chem. Soc. Perkin Trans = US 4,517,359 1, 1986, 1881 = J. Chem. Res., 1988, 132 S. Djokic PLIVA
= Idem miniprint., 1988, 1239 B b) US 4,474,768 G.M. Bright PFIZER
C c) US 5,686,587 d) EP 0,699,207 B.V. Yang PFIZER
e) ES 2,104,386 D f) US 5,869,629 = J.Org.Chem, .1997, 62, '(21), g) EP 0,827,965 7479 - 7481 M. Bayod ASTUR PHARMA
h) ES 2,122,905 = Magn. Reson. Chem, 1998, 36, 217-225 E i) EP 0,879,823 W. Heggie HOVIONE
The structural elucidation studies carried out with azithromycin 1 have shown the existence of two different crystalline forms: hygroscopic monohydrate and non-hygroscopic dihydrate, being the latter preferred for manufacturing formulations used in therapeutical treatments, as it is described in EP 0,298,650.
Azithromycin dihydrate is easily distinguishable. from hygroscopic azithromycin by means of the following differentiative assays:
a) The dihydrate form keeps its percentile water content constant at values (4.5-5%) which are very close to the theoretical value (4.6%).
b) The differential calorimetry analysis (DSC) of azithromycin dihydrate reveals the presence of a single endotherm which may vary between 115 and 13 5 C, with an energy absorbed during the process which ranges between 27 and 34 cal/g.
c) Each crystalline form presents its own characteristic X-Ray Diffraction spectrum.
d) The infrared spectra in KBr of both crystalline forms present clear differences:
azithrom cin dihydrate azithrom cin monoh drate v (cm"' v (cm") 3560 and 3496 (2 sharp bands) 3500 (wide band) 1344 Does not present any 1282 and 1268 (2 sharp bands 1280 1083 Does not present any Two other synthesis, affording azithromycin 1 as a form that should differ from the crystalline ones previously mentioned, have also been described. In these cases, azithromycin is obtained by simple evaporation to dryness. However, in these documents there is no reference to the crystalline state of the azithromycin thus obtained.
Patent Applicant Priority Procedure (Author) = WO 94/26758 PFIZER May 19,1993 Methylene chloride evaporation a) US 5,686,587 (B.V. Yang) b) EP 0,699,207 c) ES 2,104,386 = BE 892,357 PLIVA Mar. 3, 1981 Chloroform evaporation = US 4,517,359 (S. Djokic) In the following table are summarized the different procedures for the preparation of both crystalline forms of azithromycin 1.
Crystalline form Patent (Author) Applicant Priority Procedure HYGROSCOPIC a) EP 0,101,186 PFIZER July 19, 1982 Recrystallization from MONOHYDRATE b) US 4,474,768 (G.M. Biight) ethanol/water HYGROSCOPIC c) EP 0,298,650 PFIZER July 9, 1997 Recrystallization from MONOHYDRATE (D. Allen) ethanol/water NON- d) EP 0,298,650 PFIZER Recrystallization from HYGROSCOPIC e) WO 89/00576 July 9, 1997 THF / petroleum ether/
DIHYDRATE f) ES 2,038,756 ~' ~1~) water = Recrystallization from acetone/water NON- g) CN 1,093,370 Faming = Recrystallization from HYGROSCOPIC (Chem. Abs. Zhuanli.... Dec. 10, 1993 other solvents DIHYDRATE 29525q,124,1996) (Q. Song) (methanol, DMF, acetonitrile, dioxane, ... ) and water NON- CHEMO- Recrystallization from HYGROSCOPIC h) EC 95-1389 TECNICA May, 1995 acetone/ water DIHYDRATE SINTYAL
NON- i) EP 0,827,965 ASTUR Recrystallization from HYGROSCOPIC j) ES 2,122,905 PHARMA July 11, 1996 acetone/ water DIHYDRATE k) US 5,869,629 (M.Bayod) NON- Precipitation from a base HYGROSCOPIC 1) EP 0,941,999 HOVIONE Mar. 13, 1998 neutralized acid solution of DIHYDRATE (W=Heggie) azithromycin in acetone/ water Crystalline form Article Author Date Procedure Two recrystallizations:
J. Chem. Res., 1. Precipitation from a NON- = 1988, 132 S.Djokic May, 1988 base neutralized acid HYGROSCOPIC m) idem miniprint., (PLIVA) (received solution of azithromycin in DIHYDRATE 1988, 1239, June 4, 1987) acetone/ water.
2. From ethyl ether:
NON- = J. Org. Chem, M.Bayod Nov., 1997 Recrystallization from HYGROSCOPIC 1997, 62, (21), (ASTUR- (received acetone/water DIHYDRATE 7479 - 7481 PHARMA) May 1, 1997) HYGROSCOPIC = J. Org. Chem, M.Bayod Nov., 1997 Recrystallization from MONOHYDRATE 1997, 62, (21), (ASTUR (received ethanol/water 7479 - 7481 PHARMA) May 1, 1997) 3a SUMMARY OF INVENTION
In a first aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining the solution with water; thereby crystallizing Azithromycin as the crystalline dihydrate form.
In a second aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining the solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
In a third aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
hydrolyzing 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homoerythromycin A 11, 1 2-hydrogenorthoborate in an organic solvent by contacting the 9-deoxo-9a-aza-11, 1 2-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving the Azithromycin in tert-butanol to form a solution; and combining the solution with water, thereby crystallizing Azithromycin as the crystalline dihydrate form.
In a fourth aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
3b hydrolyzing 9-deoxo-9a-aza- 11, 1 2-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate in an organic solvent by contacting the 9-deoxo-9a-aza-11, 1 2-desoxy-9a-methyl-9a-homoerythromycin A 11, 1 2-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving the Azithromycin in tert-butanol to form a solution; and combining the solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
The organic solvent used in the method of the third and fourth aspect of the present invention can be ethyl acetate, acetonitrile, methanol, or ethanol.
Furthermore, the dilute acid used in the method of the third and fourth aspect of the present invention can be dilute sulfuric acid, dilute hydrochloric acid, or dilute oxalic acid.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the different synthetic routes to azithromycin.
FIG. 2 shows the infrared spectra of non-crystalline azithromycin and crystalline azithromycin dihydrate recorded in FT-IR Nicolet Impact 410 Instrument.
FIG. 3 shows the thermograms of non-crystalline azithromycin and crystalline azithromycin dihydrate obtained scanning between 20 and 300 C, under nitrogen with a heating rate of 5 C/min.
FIG. 4 shows X-ray diffraction spectra of non-crystalline azithromycin and crystalline azithromycin dihydrate recorded on a Philips PW1710 diffractometer.
DESCRIPTION OF THE INVENTION.
First, the present invention provides a series of new procedures for the preparation of azithromycin 1:
= A procedure for the preparation of its crystalline dihydrate form, characterized by crystallization. of azithromycin from a mixture of tert-butanol / water: In this procedure crystalline azithromycin monohydrate is dissolved in tert-butanol and, after water addition, is allowed to crystallize for a period of 48-72 hours.
= A procedure for the preparation of its crystalline dihydrate form, characterized by crystallization of azithromycin from a mixture of tert-butanol / petroleum ether /
water. In this procedure, crystalline azithromycin monohydrate is dissolved in tert-butanol and added to a mixture of petroleum ether and water. This solution is allowed to crystallize for a period of 48-12 hours.
= A procedure for the preparation of non-crystalline azithromycin by means of lyophilization of solutions of azithromycin in tert-butanol (2-methyl-2-propanol).
= A procedure for the preparation of non-crystalline azithromycin by means of evaporation of solutions of azithromycin in aliphatic alcohols (preferably ethanol or isopropanol).
Secondly, the present invention describes the characterization of non-crystalline azithromycin and its unambiguous differentiation from the crystalline forms (dihydrate and monohydrate) using the following techniques:
/ Infrared Spectroscopy / Differential Scan Calorimetry (DSC) / X-Ray Diffraction / Hygroscopicity / Crystallinity test by means of polarized light microscopy The procedures which are the object of the present invention are advantageous over previously described methods, essentially at industrial scale:
/ Lyophilization is a technique that guarantees excellent results concerning homogeneity, purity and consistency of analytical data of different batches.
/ The crystallization procedures, which are characterized by slow crystal growth, greatly improve the homogeneity and particle distribution of different batches. This minimizes the presence of the non-crystalline fraction (detected by X-Ray and DSC) that is always present in crystalline azithromycin dihydrate obtained by the methods reported in the literature and above cited.
The differences observed between crystalline azithromycin dihydrate and its non-5 crystalline form, using the techniques previously mentioned, are shown below:
1. Infrared Spectra (KBr), recorded in a FT-IR Nicolet Impact 410 Instrument, of both azithromycin forms are clearly different. Fig. 2 reproduces the spectra which most significative bands are summarized in the following table:
C stalline azithromycin dihydrate Non-crystalline azithromycin v crri 1) v (cm-1 3561 and 3496 (2 sharp bands) 3500 (wide band) 1344 Does not present an1282, 1269 and 1251 3 sharp bands) 1280 and 1257 2 sharp bands) 1083 Does not present any 2. DSC. In Fig. 3 are shown the thermograms obtained scanning between 20 and 300'C, under nitrogen with a heating rate of 5*C / min. The thermogram of the non-crystalline form does not present any melting peak, what clearly differentiates it from the one corresponding to crystalline azithromycin dihydrate.
3. X-Ray Diffraction Spectra were recorded on a Philips PW 1710 diffractometer. As the spectrum corresponding to non-crystalline azithromycin (Fig. 4) is characterized by the absence of defined maxima, this solid is considered to be amorphous.
4. Hygroscopicity. Two different samples of non-crystalline azithromycin containing 3%
water were kept under an atmosphere over 75% relative humidity. After 8 hours, water content in the first sample was 5.3%, while the second one contained 9.9%
water after 72 hours. Non-crystalline azithromycin is thus moderately hygroscopic.
5. Crystallinity tests (polarized light microscopy) carried out with non-crystalline azithromycin were negative, as their particles do not show birefringence.
EXPERIMENTAL PART
= Preparation of 9-deoxo-9a-aza-11,12-desoxy-9a-homoerythromycin A 11,12-hydrogenorthoborate.
89 g of 9-deoxo-6-desoxy-6,9-epoxy-9,9a-dihydro-9a-aza-homoerythromycin A are dissolved in 450 ml of methanol and cooled down between -5 and -10 C. While keeping the temperature in the specified interval 16 portions of 2.2 g each of sodium borohydride are added. Temperature and stirring conditions are maintained for two additional hours and the bulk of the reaction is allowed to reach 20 C. After 20 h, the methanol is evaporated to dryness. The residue is dissolved in 500 ml of methylene chloride and 750 ml of water and shaked for 30 min. The organic phase is separated and the aqueous phase is extracted with 250 ml of methylene chloride. The organic phases are combined, filtered over celite, dried with anhydrous sodium sulphate and concentrated to dryness to yield 85 g of 9-deoxo-9a-aza-11,12-desoxy-9a-homoerythromycin A 11,12-hydrogenorthoborate.
IR (KBr) v.= 3500, 2980, 2960, 1730, 1470, 1390, 1170, 1090, 1060 cm' 1H-NMR (CDC13) S= 2.21 (NMe2),3.27 (OMe) ppm.
(~artial) ~ C-NMR (CDC13) 8= 180.0 (C=O), 79.63 (ClI), 76.46 (C12) 58.7 (Clo), 57.1(C9), 49.4 (rartial) (OMe), 40.2 (NMe2) ppm ' B-NMR (CDC13) 8= 9.9 ppm ai %= 200 Hz TLC rf = 0.28 (petroleum ether : ethyl acetate : diethylamine 75:25:10) developer: ethanol/vanillin (sulphuric acid) = Preparation of 9-deoxo-9 a-aza-1 1,12-desoxy-9a-methyl-9a-homo-erythromycin A 11,12-hydrogenorthoborate.
50 g of 9-deoxo-9a-aza-11,12-desoxy-9a-homoerythromycin A 11,12-hydrogenortho-borate are dissolved in 500 ml of chloroform, and subsequently a mixture of 5.5 ml of formic acid and 11.75 ml of aqueous 35-40% formaldehyde is added. The reaction mixture is heated under pressure for 14 hours and subsequently cooled down to 15-20 C.
500 ml of water are added and the mixture is taken to pH=4 by adding 20%
sulphuric acid. The mixture is shaken for 15 min and the lower organic layer is separated. The alkaline aqueous phase is extracted with 2x 100 ml methylene chloride. The organic phases are combined and filtered over celite, dried with anhydrous sodium sulfate and evaporated to dryness. The residue obtained is washed twice with 250 ml of ethyl ether, yielding a dry residue of 29 g of 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homo-erythromycin A 11,12-hydrogenorthoborate.
...._.,-- -.~~.~
IR (KBr) v,,W= 3500, 1730, 1470, 1390, 1090, 1070 cm'' 'H-NMR (CDC13) S= 2.00 (NMeZ), 2.30 (NMe), 3.37 (OMe) ppm.
(~artial) 1 C-NMR (CDC13) S= 179.9 (C=O), 79.40 (C>>), 77.09 (C12), 68.84 (Cy), 64.08 (Cio), 49.36 (partial) (OMe), 40.18 (NMe2), 34.39 (NMe) ppm "B-1VMR (CDC13) S= 10.1 ppm w 180 Hz m/e M+= 775.5 TLC rf = 0.38 (petroleum ether : ethyl acetate : diethylamine 75:25:10) developer: ethanol/vanillin (sulphuric acid) = Hydrolysis of 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homo-erythromycin A
11,12-hydrogenorthoborate. Synthesis of 9-deoxo-9a-aza-9a-methyl-9a-homo-erythromycin A (Azithromycin).
22 g of 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homo-erythromycin A 11,12-hydrogenorthoborate are dissolved in 250 n-d of acetonitrile to which 125 ml of water are subsequently added. 20% sulphuric acid is added to the mixture to take it to pH=2, and stirring is maintained for 30 min. The acidic solution is poured into a mixture of 350 ml of methylene chloride and 350 ml of water, inmediately adding 48% lime until pH=9. The mixture is shaken for 15 min and the lower organic phase is separated. The alkaline aqueous phase is extracted with 2x100 ml of methylene chloride. The combined organic phases are filtered over celite and evaporated to dryness. The residue is dissolved in 50 ml of ethanol and 60 ml of water are added over 30 min. Precipitation is allowed for 2 h, and the solid is collected by filtration and vacuum-dried at 40 C to yield 15 g of 9-deoxo-9a-aza-9a-methyl-9a-homo-erythromycin A (Azithromycin).
IR (KBr) v,,.= 3500, 3000, 2970, 1740, 1470, 1380, 1280, 1060 cm'' 1H-13Nnt (CDC13) S= 2.31 (NMe.Z), 2.34 (NMe), 3.38 (OMe) ppm (partial) ' C-NNIR (CDC13) S= 178.9 (C=O), 73.08 (C12), 72.32 (Cõ), 69.88 (C9), 62.43 (Clo), 49.37 (partial) (OMe), 40.23 (1VMe2), 35.92 (NMe) ppm m/e M+= 749.5 I-IPLC corresponds according to USP XXIII
TLC rf= 0.62 (petroleum ether : ethyl acetate : diethylamine 75:25:10) developer: ethanol/vanillin (sulphuric acid) = Preparation of 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A dihydrate.
Method A.
25 g of crystalline azithromycin monohydrate are dissolved in 130 ml of tert-butanol heating at 30'C. This solution, is filtered and 130 ml of water are added over 6 h. The resulting mixture is taken to pH=i 1 by addition of NaOH 2N, cooled down below 8 and subsequently stirred for 48-72 h. The crystals are collected by filtration and dried (80 mm Hg / 25 *C) to yield 15 g of azithromycin dihydrate.
IR (KBr) v = 3560, 3496, 1740, 1470, 1380, 1344, 1282, 1268, 1251, 1093 cm' 'H-NMR (CDC13), "C-NMR (CDC13), m/e, TLC and HPLC are identical to those of the previous example.
= Preparation of 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A dihydrate.
Method B.
25 g of crystalline azithromycin monohydrate are dissolved in 50 ml of tert-butanol heating at 30 C. This solution is filtered and discharged over a mixture of 500 ml of petroleum ether and 20 ml of water. The resulting mixture is cooled down below and subsequently stirred for 48-72 h. The crystals are collected by filtration and dried (80 mm Hg / 25 *C) to yield 12 g of azithromycin dihydrate.
IR (KBr),'H-1VMR (CDC13), t'C-NMR (CDC13), m/e, TLC and HPLC are identical to those of the previous example.
~ Preparation of non-crystalline 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A. Method A.
5 g of crystalline azithromycin monohydrate are dissolved in 25 ml of tert-butanol heating at 30 C. This solution is filtered and solidified in a cooling bath.
The solvent is sublimed at room temperature and 10-2mm Hg. The solid obtained is dried (80 mm Hg /
40 *C) to yield 5 g of non-crystalline azithromycin.
IR (KBr) v.= 3500, 1740, 1470, 1280, 1268, 1257 cm"'(See Fig. 2) 'H-N1vIR (CDC13),13C-NMR (CDC13), m/e, TLC and HPLC are identical to those of the previous example % H20 (K.F.)= 3.0 %
DSC = See Fig. 3 X-Ray Diffraction = See Fig. 4 = Preparation of non-crystalline 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A. Method B.
5 g of crystalline azithromycin monohydrate are dissolved in 25 ml of ethanol.
The solution is filtered and the solvent evaporated at room temperature and 150 mm Hg. The solid obtained is dried (80 mm Hg / 40 *C) to yield 5 g of non-crystalline azithromycin, which analytical data are identical to those of the previous example.
Route Patents Articles Author Applicant A a) US 4,328,334 = J. Chem. Soc. Perkin Trans = US 4,517,359 1, 1986, 1881 = J. Chem. Res., 1988, 132 S. Djokic PLIVA
= Idem miniprint., 1988, 1239 B b) US 4,474,768 G.M. Bright PFIZER
C c) US 5,686,587 d) EP 0,699,207 B.V. Yang PFIZER
e) ES 2,104,386 D f) US 5,869,629 = J.Org.Chem, .1997, 62, '(21), g) EP 0,827,965 7479 - 7481 M. Bayod ASTUR PHARMA
h) ES 2,122,905 = Magn. Reson. Chem, 1998, 36, 217-225 E i) EP 0,879,823 W. Heggie HOVIONE
The structural elucidation studies carried out with azithromycin 1 have shown the existence of two different crystalline forms: hygroscopic monohydrate and non-hygroscopic dihydrate, being the latter preferred for manufacturing formulations used in therapeutical treatments, as it is described in EP 0,298,650.
Azithromycin dihydrate is easily distinguishable. from hygroscopic azithromycin by means of the following differentiative assays:
a) The dihydrate form keeps its percentile water content constant at values (4.5-5%) which are very close to the theoretical value (4.6%).
b) The differential calorimetry analysis (DSC) of azithromycin dihydrate reveals the presence of a single endotherm which may vary between 115 and 13 5 C, with an energy absorbed during the process which ranges between 27 and 34 cal/g.
c) Each crystalline form presents its own characteristic X-Ray Diffraction spectrum.
d) The infrared spectra in KBr of both crystalline forms present clear differences:
azithrom cin dihydrate azithrom cin monoh drate v (cm"' v (cm") 3560 and 3496 (2 sharp bands) 3500 (wide band) 1344 Does not present any 1282 and 1268 (2 sharp bands 1280 1083 Does not present any Two other synthesis, affording azithromycin 1 as a form that should differ from the crystalline ones previously mentioned, have also been described. In these cases, azithromycin is obtained by simple evaporation to dryness. However, in these documents there is no reference to the crystalline state of the azithromycin thus obtained.
Patent Applicant Priority Procedure (Author) = WO 94/26758 PFIZER May 19,1993 Methylene chloride evaporation a) US 5,686,587 (B.V. Yang) b) EP 0,699,207 c) ES 2,104,386 = BE 892,357 PLIVA Mar. 3, 1981 Chloroform evaporation = US 4,517,359 (S. Djokic) In the following table are summarized the different procedures for the preparation of both crystalline forms of azithromycin 1.
Crystalline form Patent (Author) Applicant Priority Procedure HYGROSCOPIC a) EP 0,101,186 PFIZER July 19, 1982 Recrystallization from MONOHYDRATE b) US 4,474,768 (G.M. Biight) ethanol/water HYGROSCOPIC c) EP 0,298,650 PFIZER July 9, 1997 Recrystallization from MONOHYDRATE (D. Allen) ethanol/water NON- d) EP 0,298,650 PFIZER Recrystallization from HYGROSCOPIC e) WO 89/00576 July 9, 1997 THF / petroleum ether/
DIHYDRATE f) ES 2,038,756 ~' ~1~) water = Recrystallization from acetone/water NON- g) CN 1,093,370 Faming = Recrystallization from HYGROSCOPIC (Chem. Abs. Zhuanli.... Dec. 10, 1993 other solvents DIHYDRATE 29525q,124,1996) (Q. Song) (methanol, DMF, acetonitrile, dioxane, ... ) and water NON- CHEMO- Recrystallization from HYGROSCOPIC h) EC 95-1389 TECNICA May, 1995 acetone/ water DIHYDRATE SINTYAL
NON- i) EP 0,827,965 ASTUR Recrystallization from HYGROSCOPIC j) ES 2,122,905 PHARMA July 11, 1996 acetone/ water DIHYDRATE k) US 5,869,629 (M.Bayod) NON- Precipitation from a base HYGROSCOPIC 1) EP 0,941,999 HOVIONE Mar. 13, 1998 neutralized acid solution of DIHYDRATE (W=Heggie) azithromycin in acetone/ water Crystalline form Article Author Date Procedure Two recrystallizations:
J. Chem. Res., 1. Precipitation from a NON- = 1988, 132 S.Djokic May, 1988 base neutralized acid HYGROSCOPIC m) idem miniprint., (PLIVA) (received solution of azithromycin in DIHYDRATE 1988, 1239, June 4, 1987) acetone/ water.
2. From ethyl ether:
NON- = J. Org. Chem, M.Bayod Nov., 1997 Recrystallization from HYGROSCOPIC 1997, 62, (21), (ASTUR- (received acetone/water DIHYDRATE 7479 - 7481 PHARMA) May 1, 1997) HYGROSCOPIC = J. Org. Chem, M.Bayod Nov., 1997 Recrystallization from MONOHYDRATE 1997, 62, (21), (ASTUR (received ethanol/water 7479 - 7481 PHARMA) May 1, 1997) 3a SUMMARY OF INVENTION
In a first aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining the solution with water; thereby crystallizing Azithromycin as the crystalline dihydrate form.
In a second aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining the solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
In a third aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
hydrolyzing 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homoerythromycin A 11, 1 2-hydrogenorthoborate in an organic solvent by contacting the 9-deoxo-9a-aza-11, 1 2-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving the Azithromycin in tert-butanol to form a solution; and combining the solution with water, thereby crystallizing Azithromycin as the crystalline dihydrate form.
In a fourth aspect, the present invention provides a method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A (Azithromycin) in a crystalline dihydrate form, the method comprising:
3b hydrolyzing 9-deoxo-9a-aza- 11, 1 2-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate in an organic solvent by contacting the 9-deoxo-9a-aza-11, 1 2-desoxy-9a-methyl-9a-homoerythromycin A 11, 1 2-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving the Azithromycin in tert-butanol to form a solution; and combining the solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
The organic solvent used in the method of the third and fourth aspect of the present invention can be ethyl acetate, acetonitrile, methanol, or ethanol.
Furthermore, the dilute acid used in the method of the third and fourth aspect of the present invention can be dilute sulfuric acid, dilute hydrochloric acid, or dilute oxalic acid.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the different synthetic routes to azithromycin.
FIG. 2 shows the infrared spectra of non-crystalline azithromycin and crystalline azithromycin dihydrate recorded in FT-IR Nicolet Impact 410 Instrument.
FIG. 3 shows the thermograms of non-crystalline azithromycin and crystalline azithromycin dihydrate obtained scanning between 20 and 300 C, under nitrogen with a heating rate of 5 C/min.
FIG. 4 shows X-ray diffraction spectra of non-crystalline azithromycin and crystalline azithromycin dihydrate recorded on a Philips PW1710 diffractometer.
DESCRIPTION OF THE INVENTION.
First, the present invention provides a series of new procedures for the preparation of azithromycin 1:
= A procedure for the preparation of its crystalline dihydrate form, characterized by crystallization. of azithromycin from a mixture of tert-butanol / water: In this procedure crystalline azithromycin monohydrate is dissolved in tert-butanol and, after water addition, is allowed to crystallize for a period of 48-72 hours.
= A procedure for the preparation of its crystalline dihydrate form, characterized by crystallization of azithromycin from a mixture of tert-butanol / petroleum ether /
water. In this procedure, crystalline azithromycin monohydrate is dissolved in tert-butanol and added to a mixture of petroleum ether and water. This solution is allowed to crystallize for a period of 48-12 hours.
= A procedure for the preparation of non-crystalline azithromycin by means of lyophilization of solutions of azithromycin in tert-butanol (2-methyl-2-propanol).
= A procedure for the preparation of non-crystalline azithromycin by means of evaporation of solutions of azithromycin in aliphatic alcohols (preferably ethanol or isopropanol).
Secondly, the present invention describes the characterization of non-crystalline azithromycin and its unambiguous differentiation from the crystalline forms (dihydrate and monohydrate) using the following techniques:
/ Infrared Spectroscopy / Differential Scan Calorimetry (DSC) / X-Ray Diffraction / Hygroscopicity / Crystallinity test by means of polarized light microscopy The procedures which are the object of the present invention are advantageous over previously described methods, essentially at industrial scale:
/ Lyophilization is a technique that guarantees excellent results concerning homogeneity, purity and consistency of analytical data of different batches.
/ The crystallization procedures, which are characterized by slow crystal growth, greatly improve the homogeneity and particle distribution of different batches. This minimizes the presence of the non-crystalline fraction (detected by X-Ray and DSC) that is always present in crystalline azithromycin dihydrate obtained by the methods reported in the literature and above cited.
The differences observed between crystalline azithromycin dihydrate and its non-5 crystalline form, using the techniques previously mentioned, are shown below:
1. Infrared Spectra (KBr), recorded in a FT-IR Nicolet Impact 410 Instrument, of both azithromycin forms are clearly different. Fig. 2 reproduces the spectra which most significative bands are summarized in the following table:
C stalline azithromycin dihydrate Non-crystalline azithromycin v crri 1) v (cm-1 3561 and 3496 (2 sharp bands) 3500 (wide band) 1344 Does not present an1282, 1269 and 1251 3 sharp bands) 1280 and 1257 2 sharp bands) 1083 Does not present any 2. DSC. In Fig. 3 are shown the thermograms obtained scanning between 20 and 300'C, under nitrogen with a heating rate of 5*C / min. The thermogram of the non-crystalline form does not present any melting peak, what clearly differentiates it from the one corresponding to crystalline azithromycin dihydrate.
3. X-Ray Diffraction Spectra were recorded on a Philips PW 1710 diffractometer. As the spectrum corresponding to non-crystalline azithromycin (Fig. 4) is characterized by the absence of defined maxima, this solid is considered to be amorphous.
4. Hygroscopicity. Two different samples of non-crystalline azithromycin containing 3%
water were kept under an atmosphere over 75% relative humidity. After 8 hours, water content in the first sample was 5.3%, while the second one contained 9.9%
water after 72 hours. Non-crystalline azithromycin is thus moderately hygroscopic.
5. Crystallinity tests (polarized light microscopy) carried out with non-crystalline azithromycin were negative, as their particles do not show birefringence.
EXPERIMENTAL PART
= Preparation of 9-deoxo-9a-aza-11,12-desoxy-9a-homoerythromycin A 11,12-hydrogenorthoborate.
89 g of 9-deoxo-6-desoxy-6,9-epoxy-9,9a-dihydro-9a-aza-homoerythromycin A are dissolved in 450 ml of methanol and cooled down between -5 and -10 C. While keeping the temperature in the specified interval 16 portions of 2.2 g each of sodium borohydride are added. Temperature and stirring conditions are maintained for two additional hours and the bulk of the reaction is allowed to reach 20 C. After 20 h, the methanol is evaporated to dryness. The residue is dissolved in 500 ml of methylene chloride and 750 ml of water and shaked for 30 min. The organic phase is separated and the aqueous phase is extracted with 250 ml of methylene chloride. The organic phases are combined, filtered over celite, dried with anhydrous sodium sulphate and concentrated to dryness to yield 85 g of 9-deoxo-9a-aza-11,12-desoxy-9a-homoerythromycin A 11,12-hydrogenorthoborate.
IR (KBr) v.= 3500, 2980, 2960, 1730, 1470, 1390, 1170, 1090, 1060 cm' 1H-NMR (CDC13) S= 2.21 (NMe2),3.27 (OMe) ppm.
(~artial) ~ C-NMR (CDC13) 8= 180.0 (C=O), 79.63 (ClI), 76.46 (C12) 58.7 (Clo), 57.1(C9), 49.4 (rartial) (OMe), 40.2 (NMe2) ppm ' B-NMR (CDC13) 8= 9.9 ppm ai %= 200 Hz TLC rf = 0.28 (petroleum ether : ethyl acetate : diethylamine 75:25:10) developer: ethanol/vanillin (sulphuric acid) = Preparation of 9-deoxo-9 a-aza-1 1,12-desoxy-9a-methyl-9a-homo-erythromycin A 11,12-hydrogenorthoborate.
50 g of 9-deoxo-9a-aza-11,12-desoxy-9a-homoerythromycin A 11,12-hydrogenortho-borate are dissolved in 500 ml of chloroform, and subsequently a mixture of 5.5 ml of formic acid and 11.75 ml of aqueous 35-40% formaldehyde is added. The reaction mixture is heated under pressure for 14 hours and subsequently cooled down to 15-20 C.
500 ml of water are added and the mixture is taken to pH=4 by adding 20%
sulphuric acid. The mixture is shaken for 15 min and the lower organic layer is separated. The alkaline aqueous phase is extracted with 2x 100 ml methylene chloride. The organic phases are combined and filtered over celite, dried with anhydrous sodium sulfate and evaporated to dryness. The residue obtained is washed twice with 250 ml of ethyl ether, yielding a dry residue of 29 g of 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homo-erythromycin A 11,12-hydrogenorthoborate.
...._.,-- -.~~.~
IR (KBr) v,,W= 3500, 1730, 1470, 1390, 1090, 1070 cm'' 'H-NMR (CDC13) S= 2.00 (NMeZ), 2.30 (NMe), 3.37 (OMe) ppm.
(~artial) 1 C-NMR (CDC13) S= 179.9 (C=O), 79.40 (C>>), 77.09 (C12), 68.84 (Cy), 64.08 (Cio), 49.36 (partial) (OMe), 40.18 (NMe2), 34.39 (NMe) ppm "B-1VMR (CDC13) S= 10.1 ppm w 180 Hz m/e M+= 775.5 TLC rf = 0.38 (petroleum ether : ethyl acetate : diethylamine 75:25:10) developer: ethanol/vanillin (sulphuric acid) = Hydrolysis of 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homo-erythromycin A
11,12-hydrogenorthoborate. Synthesis of 9-deoxo-9a-aza-9a-methyl-9a-homo-erythromycin A (Azithromycin).
22 g of 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homo-erythromycin A 11,12-hydrogenorthoborate are dissolved in 250 n-d of acetonitrile to which 125 ml of water are subsequently added. 20% sulphuric acid is added to the mixture to take it to pH=2, and stirring is maintained for 30 min. The acidic solution is poured into a mixture of 350 ml of methylene chloride and 350 ml of water, inmediately adding 48% lime until pH=9. The mixture is shaken for 15 min and the lower organic phase is separated. The alkaline aqueous phase is extracted with 2x100 ml of methylene chloride. The combined organic phases are filtered over celite and evaporated to dryness. The residue is dissolved in 50 ml of ethanol and 60 ml of water are added over 30 min. Precipitation is allowed for 2 h, and the solid is collected by filtration and vacuum-dried at 40 C to yield 15 g of 9-deoxo-9a-aza-9a-methyl-9a-homo-erythromycin A (Azithromycin).
IR (KBr) v,,.= 3500, 3000, 2970, 1740, 1470, 1380, 1280, 1060 cm'' 1H-13Nnt (CDC13) S= 2.31 (NMe.Z), 2.34 (NMe), 3.38 (OMe) ppm (partial) ' C-NNIR (CDC13) S= 178.9 (C=O), 73.08 (C12), 72.32 (Cõ), 69.88 (C9), 62.43 (Clo), 49.37 (partial) (OMe), 40.23 (1VMe2), 35.92 (NMe) ppm m/e M+= 749.5 I-IPLC corresponds according to USP XXIII
TLC rf= 0.62 (petroleum ether : ethyl acetate : diethylamine 75:25:10) developer: ethanol/vanillin (sulphuric acid) = Preparation of 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A dihydrate.
Method A.
25 g of crystalline azithromycin monohydrate are dissolved in 130 ml of tert-butanol heating at 30'C. This solution, is filtered and 130 ml of water are added over 6 h. The resulting mixture is taken to pH=i 1 by addition of NaOH 2N, cooled down below 8 and subsequently stirred for 48-72 h. The crystals are collected by filtration and dried (80 mm Hg / 25 *C) to yield 15 g of azithromycin dihydrate.
IR (KBr) v = 3560, 3496, 1740, 1470, 1380, 1344, 1282, 1268, 1251, 1093 cm' 'H-NMR (CDC13), "C-NMR (CDC13), m/e, TLC and HPLC are identical to those of the previous example.
= Preparation of 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A dihydrate.
Method B.
25 g of crystalline azithromycin monohydrate are dissolved in 50 ml of tert-butanol heating at 30 C. This solution is filtered and discharged over a mixture of 500 ml of petroleum ether and 20 ml of water. The resulting mixture is cooled down below and subsequently stirred for 48-72 h. The crystals are collected by filtration and dried (80 mm Hg / 25 *C) to yield 12 g of azithromycin dihydrate.
IR (KBr),'H-1VMR (CDC13), t'C-NMR (CDC13), m/e, TLC and HPLC are identical to those of the previous example.
~ Preparation of non-crystalline 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A. Method A.
5 g of crystalline azithromycin monohydrate are dissolved in 25 ml of tert-butanol heating at 30 C. This solution is filtered and solidified in a cooling bath.
The solvent is sublimed at room temperature and 10-2mm Hg. The solid obtained is dried (80 mm Hg /
40 *C) to yield 5 g of non-crystalline azithromycin.
IR (KBr) v.= 3500, 1740, 1470, 1280, 1268, 1257 cm"'(See Fig. 2) 'H-N1vIR (CDC13),13C-NMR (CDC13), m/e, TLC and HPLC are identical to those of the previous example % H20 (K.F.)= 3.0 %
DSC = See Fig. 3 X-Ray Diffraction = See Fig. 4 = Preparation of non-crystalline 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A. Method B.
5 g of crystalline azithromycin monohydrate are dissolved in 25 ml of ethanol.
The solution is filtered and the solvent evaporated at room temperature and 150 mm Hg. The solid obtained is dried (80 mm Hg / 40 *C) to yield 5 g of non-crystalline azithromycin, which analytical data are identical to those of the previous example.
Claims (8)
1. A method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A
(Azithromycin) in a crystalline dihydrate form, said method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining said solution with water; thereby crystallizing Azithromycin as the crystalline dihydrate form.
(Azithromycin) in a crystalline dihydrate form, said method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining said solution with water; thereby crystallizing Azithromycin as the crystalline dihydrate form.
2. A method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A
(Azithromycin) in a crystalline dihydrate form, said method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining said solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
(Azithromycin) in a crystalline dihydrate form, said method comprising:
dissolving Azithromycin in tert-butanol to form a solution; and combining said solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
3. A method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A
(Azithromycin) in a crystalline dihydrate form, said method comprising:
hydrolyzing 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate in an organic solvent by contacting said 9-deoxo-9a-aza- 11, 12-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving said Azithromycin in tert-butanol to form a solution; and combining said solution with water, thereby crystallizing Azithromycin as the crystalline dihydrate form.
(Azithromycin) in a crystalline dihydrate form, said method comprising:
hydrolyzing 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate in an organic solvent by contacting said 9-deoxo-9a-aza- 11, 12-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving said Azithromycin in tert-butanol to form a solution; and combining said solution with water, thereby crystallizing Azithromycin as the crystalline dihydrate form.
4. The method of claim 3, wherein the organic solvent is selected from the group consisting of ethyl acetate, acetonitrile, methanol, and ethanol.
5. The method of claim 3, wherein the dilute acid is selected from the group consisting of dilute sulfuric acid, dilute hydrochloric acid, and dilute oxalic acid.
6. A method of preparing 9-deoxo-9a-aza-9a-methyl-9a-homoerythromycin A
(Azithromycin) in a crystalline dihydrate form, said method comprising:
hydrolyzing 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate in an organic solvent by contacting said 9-deoxo-9a-aza- 11, 12-desoxy-9a-methyl-9a-homoerythromycin A 11, 12-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving said Azithromycin in tert-butanol to form a solution; and combining said solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
(Azithromycin) in a crystalline dihydrate form, said method comprising:
hydrolyzing 9-deoxo-9a-aza-11,12-desoxy-9a-methyl-9a-homoerythromycin A 11,12-hydrogenorthoborate in an organic solvent by contacting said 9-deoxo-9a-aza- 11, 12-desoxy-9a-methyl-9a-homoerythromycin A 11, 12-hydrogenorthoborate with a dilute acid at room temperature and at a pH range between 2 and 4, thereby producing Azithromycin;
dissolving said Azithromycin in tert-butanol to form a solution; and combining said solution with a mixture of water and petroleum ether, thereby crystallizing Azithromycin as the crystalline dihydrate form.
7. The method of claim 6, wherein the organic solvent is selected from the group consisting of ethyl acetate, acetonitrile, methanol, and ethanol.
8. The method of claim 6, wherein the dilute acid is selected from the group consisting of dilute sulfuric acid, dilute hydrochloric acid, and dilute oxalic acid.
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| ES9902620 | 1999-11-26 | ||
| ES009902620A ES2177373B1 (en) | 1999-11-26 | 1999-11-26 | PREPARATION OF AZITHROMYCIN IN ITS NON-CRYSTALLINE FORM |
| CA002326930A CA2326930C (en) | 1999-11-26 | 2000-11-24 | Preparation of non-crystalline and crystalline dihydrate forms of azithromycin |
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