WO1998041532A1

WO1998041532A1 - Erythromycin a oxime dihydrate

Info

Publication number: WO1998041532A1
Application number: PCT/EP1998/001430
Authority: WO
Inventors: Immaculada Bosch; Victor Centellas; José Diago
Original assignee: Biochemie S.A.
Priority date: 1997-03-14
Filing date: 1998-03-12
Publication date: 1998-09-24
Also published as: GB9705323D0; ES2160085A1; ES2160085B1; AR011191A1; AU6921298A

Abstract

Erythromycin A oxime in the form of a dihydrate having a water content of 4 % to 6.5 %, a process for its production and its use as an intermediate in the production of semi-synthetic macrolides of the erythromycin type.

Description

ERYTHROMYCIN A OXIME DIHYDRATE

The present invention relates to new intermediates useful in the synthesis of antibacterial macrolides, such as of the erythromycin, e.g. erythromycin A, type, e.g. roxithromycin, dirithromycin, clarithromycin, azithromycin and similar compounds.

A compound useful in the production of antibacterial macrolides, such as of the erythromycin type is, e.g. described in US 3,478,014, namely a compound of formula

OH

hereinafter designated as erythromycin A oxime. Erythomycin A is a well known, e.g. antibacterial agent.

According to EP 0 342 990 and EP 0 503 932 erythromycin A oxime is obtained in a first step in salt form and converted in a second step into erythromycin A oxime in free base form. Conversion is described to be carried out in dichloromethane as a solvent. Surprisingly we have found that erythromycin A oxime in free base form may be produced from erythromycin A oxime in salt form in water as a solvent without the use of organic solvents.

In one aspect the present invention provides a process for the production of a compound of formula I, e.g erythromycin A oxime, e.g. in in the form of a dihydrate, e.g. having a water content of 4% to 6.5%, e.g. in crystalline form, comprising converting a compound of formula I in the form of a salt into a compound of formula I in free form in water and isolating a compound of formula I in the form of a dihydrate.

Aprocess according to the present invention may be carried out as follows: A compound of formula I in the form of a salt which may be used as starting material include any possible salt e.g. a salt of a compound of formula I with an acid, such as an acid addition salt, e.g.with an organic acid, such as an aliphatic carboxylic acid, e.g., formic acid, acetic acid, propionic acid and an inorganic acid, preferably an inorganic acid, e.g. hydrochloric acid. A compound of formula I in the form of a salt may be combined in water with an agent which is suitable to set free a compound of formula I from the salt form, e.g. by adjustment of the pH to an appropriate value, e.g. to about 8 to 10.5 as e.g. described below in case of use of a salt of formula I with an acid. The pH may be adjusted e.g. as conventional.

If a compound of formula I in the form of a salt with an acid is used, an appropriate base may be used for pH adjustment. An appropriate base includes, for example, an inorganic base, such as, for example an alkali, e.g. sodium, potassium; earth alkali, e.g. calcium, magnesium; and ammonium; hydroxide, carbonate, bicarbonate; and an organic base, such as ammonia and an amine, e.g an alkyl amine. A base may be preferably a hydroxide, e.g. sodium and ammonia; preferably in aqueous solution; and an alkyl amine, e.g. for example triethylamine or diisopropylamine. The base may be added, for example, in aqueous solution, e.g. in about 10% to 35%, such as 15% to 30% aqueous solution. The base may, e.g. be combined with a compound of formula I in salt form by addition to a solution or suspension of a compound of formula I in salt form in water. The suspension or solution of a compound of formula I may be an aqueous solution or suspension with or without an organic solvent present; one or more organic solvents miscible or immiscible with water may be present, if desired; the presence of a small amount of organic solvent may be preferred, e.g. an organic solvent which may increase solubility of the starting material of e. g. a compound of formula I in the form of a salt; provided that a compound of formula I in free base form is still obtained in the form of a dihydrate after combination with a base. A small amount includes an amount where the water is in %v/v excess in respect with the organic solvent, such as 1 ml of organic solvent in 2 ml of water, e.g. around 4, e.g. around 6, e.g. around 8, e.g. around 10, e.g. around 20, e.g. around 30, e.g. around 50 ml of water and more. The pH of the solution or suspension of a compound of formula I in salt form may be adjusted, for example by addition of a base, e.g. as described above, to a point where a compound of formula I is present in the solution or suspension in free base form. An appropriate pH may be about 8.0 to about 10.5, e.g. 8.0 to 10.5, for example about 8.5 to about 9.5, such as 8.5 to 9.5. The temperature may be below, at, or above room temperature; such as from about 0°C to about 60°C, eg. from 0°C to 60°C; such as about 10°C to about 50°C, e.g. 10°C to 50°C, such as about 20°C to about 30°C, e.g. 20°C to 30°C. A compound of formula I in the form of a dihydrate may crystallize. The precipitate may be isolated as conventional, for example by centrifugation or filtration. A compound of formula I in the form of a dihydrate may be obtained in crystalline form.

The yields may be very high, even higher than 87%, e.g. even higher than 95%..

An isolated compound of formula I according to the present invention may have a water content in the range of about 4% to about 6.5%, e.g. 4% to 6.5%, such as about 4.2% to about 6%, e.g. 4.2% to 6%, such as about 4.5% to about 5%, e.g. 4.5% to 5% and may be identified as a crystalline dihydrate. The water content of a dihydrate according to the present invention may be, however, dependent on the storage conditions and may increase, if it is stored under appropriate, e.g. environmental, conditions. The increased addditional water content may, however, be lost again easily by drying. The differential scanning calorimetry of a compound of formula I in the form of a dihydrate may show at a heating rate of 10°C/minute an endotherm at 72.2°C; the thermal gravimetric analysis at a heating rate of 10°C/minute may show a 4.8% weight loss (onset 82.2°C - endset 114.9°C). The stoechiometric amount of water of the dihydrate is 4.7%.

Known compounds of formula I already available on the market show under the same conditions an endotherm at 123.7°C while (the small) amount of water is lost easily during the thermal gravimetric analysis.

A compound of formula I, e.g. in the form of a dihydrate, e.g. having a water content of about 4% to about 6.5%, e.g. in crystalline form according to the present invention may be dried to obtain a water content below 1 %, for example by drying at elevated temperatures; the dried compound may be prone to recover water and after some time the water content under normal environment conditions may be again of about 5%.

A compound of formula I, e.g. in the form of a dihydrate te, e.g. having a water content of about 4% to about 6.5%, e.g. in crystalline form, may be converted, if desired, into a compound of formula I having a lower water content, e.g. by - anhydrifying " in situ" directly in a solvent which may be used in a further synthetical step, for example in a reaction step to obtain a macrolide, e.g. of the erythromycin type, e.g. in high yields; - anhydrifying by dissolution in an organic solvent, concentrating the solution and isolating of the anhydrified compound of formul I.

In a preferred process of the present invention a compound of formula I in the form of a hydrochlorid may be suspended or dissolved in water and, if desired, a small amount of an organic solvent and a hydroxide, for example sodium; aqueous ammonia or an alkyl amine may be added under stirring at about room temperature, for example from 20°C to 30°C. A pH of 8.5 to 9.5 may be adjusted. A compound of formula I in the form of a dihydrate may crystallize. The precipitate may be isolated as conventional, e.g. by filtration, centrifugation.

A compound of formula I, e.g. in the form of a dihydrate, e.g. having a water content of 4% to 6.5%, e.g. in crystalline form, is new and forms also part of the present invention. In another aspect the present invention provides a compound of formula I in the form of a dihydrate, e.g. having a water content of 4% to 6.5%, e.g. in crystalline form.. X-ray powder diffraction patterns of a compound of formula I in the form of a dihydrate are given in Tables 1 to 3 below. Table 2 is more detailed than Table 1 ; and Table 3 is more detailed than Table 2.

Table 1

d (A) W₀

9.42 0.77

7.82 0.52

7.67 0.56

5.87 1.00

4.55 0.52

Table 2

d (A) I/I„ d (A) W₀

8.40 0.47 6.34 0.42

9.42 0.77 6.26 0.42

7.82 0.52 4.55 0.52

7.67 0.56 4.32 0.42

5.87 1.00 4.78 0.45

Table 3

12.66 0.1 1 6.26 0.42

1 1.16 0.08 5.87 1.00

9.42 0.77 5.46 0.38

8.40 0.47 5.34 0.18 7.82 0.52 5.04 0.20

7.67 0.56 4.78 0.45

7.37 0.29 4.55 0.52

7.17 0.30 4.32 0.42

6.83 0.39 3.64 0.19

6.34 0.42 3.55 0.25

In Tables 1 , 2 and 3 "d" denotes the interplanar spacing and "I/Io" denotes the relative intensity. The X-Ray powder diffraction patterns are determined by use of a Siemens X-Ray Powder Diffraction System D-500. Radiation λKαCu = 1.5418 Angstroem. The spectra include 4° to 60° 20 with steps of 0.05° 20 and a contact time of 3 seconds.

In another aspect the present invention provides a compound of formula I having a X- ray powder diffraction pattern of e.g. Table 1, e.g. Table 2 or e.g. Table 3.

A compound of formula I, e.g. a dihydrate, e.g. having a water content of 4% to 6.5%, e.g. in crystalline form, e.g. having an X-ray powder diffraction pattern as defined in any one of Tables 1 to 3 above, may be used as such as an intermediate in the synthesis of e.g. semi-synthetic, macrolides such as of the erythromycin e.g. A type, e.g. roxithromycin, dirithromycin, clarithromycin, azithromycin including the production of intermediates in the production of such a, e.g. semi-synthetic, macrolide. An e.g. semi- synthetic, macrolide may e.g. be produced from a compound of formula I in the form of a dihydrate as conventional in that production by use of erythromycin A oxime in another form than in the form of a dihydrate as a starting material. For example, in the production of roxithromycin the oxime hydroxy group of a compound of formula I in the form of a dihydrate may be alkylated with an appropriate group, e.g. a group of formula CH₃-O-CH₂-CH₂-O-CH₂-X, wherein X denotes a leaving group, e.g. halogen; e.g. according to a method as described in EP 33255 which is introduced herein by reference. Clarithromycin may be produced from a compound of formula I in the form of a dihydrate by selective methylation of the hydroxy group at position 6 of erythromycin A oxime, if desired after protection and subsequent removal of reactive hydroxy groups and converting the oxime group into an oxy group, e.g. as conventional, e.g. by deoximation, e.g. by treament with sodium hydrogen sulfite etc., as e.g. disclosed in EP 195 960 which is introduced herein by reference. Azithromycin may be produced from a compound of formula I, e.g. in the form of a dihydrate, e.g. having a water content of about 4% to 6.5%, via a Beckmann rearrangement and subsequent reduction, e.g. as conventional, e.g. as described in DE 30 12 533 which is introduced herein by reference, and N-methylation of a 1 l-aza-10-deoxo-lO-dihydro erythromycin A obtained, e.g. as conventional, e.g. as described in US 4,517,359 which is introduced herein by reference.

In another aspect the present invention provides the use of a compound of formula I e.g. in the form of a dihydrate, e.g. having a water content of 4% to 6.5%, e.g. in crystalline form, e.g. having an X-ray powder diffraction pattern as defined in any one of Tables 1 to 3 above, in the production of an, e.g. semi-synthetic, macrolide, such as of the erythromycin e.g. A, type, e.g. roxithromycin, dirithromycin, clarithromycin, azithromycin, preferably roxithromycin, clarithromycin, azithromycin.

In another aspect the present invention provides a process for the production of a macrolide from the erythromycin A type comprising the steps

(i) converting a compound of formula I according to claim 1 in the s form of a salt in water into a compound of formula I in the form of a dihydrate (ii) isolating a compound of formula I in the form of a dihydrate

(iii) converting a compound of formula I in the form of a dihydrate into a macrolide from the erythromycin A type, e.g. roxythromycin, dirithromycin, clarithromycin, or azithromycin, preferably roxythromycin, clarithromycin, or azithromycin, e.g. via further intermediates and a process for the production of a macrolide from the erythromycin A type comprising converting a compound of formula I in the form of a dihydrate into a macrolide from the erythromycin A type, e.g. roxythromycin, dirithromycin, clarithromycin,

In a further aspect the present invention provides a process for the production of roxythromycin wherein the hydroxy group of the oxime in a compound of formula I according to claim 1 in the form of a dihydrate, e.g. produced according to a process according to the present invention, is alkylated.

In a further aspect the present invention provides a process for the production of clarithromycin wherein the hydroxy group in position 6 of a compound of formula I according to claim 1 in the form of a dihydrate, e.g. produced according to a process according to the present invention, is methylated in position 6 and deoximated. In a further aspect the present invention provides a process for the production of azithromycin, wherein a compound of formula I according to claim 1 in the form of a dihydrate, e.g. produced according to a process according to the present invention, is rearranged via a Beckmann rearrangement and a 11 -aza- 10-deoxo- 10-dihydro erythromycin A obtained is methylated at the nitrogen atom in position 11.

A process according to the present invention is economic and ecological and may be used on industrial scale and a compound of formula I, e.g. a dihydrate, e.g. having a water content of 4% to 6.5%, e.g. in crystalline form, e.g. having an X-ray powder diffraction pattern as defined in any one of Tables 1 to 3 above, has significant advantages, e.g. any organic solvent may be avoided and the yields, e.g. in the production of a of a compound of formula I in the form of a dihydrate may be higher than 87%, e.g. higher than 95%.

The following examples illustrate the invention. All temperatures are in degrees Celsius and are uncorrected. The oxime content in the starting material and in the final product is determined by liquid chromatography (HPLC). The expression "oxime content of ....% on anhydrous basis" means that the oxime content is calculated on basis of a compound of formula I in free base and not hydrated form.Erythromycin A oxime means a compound of formula I. The compounds obtained according to the examples were identified as the oxime dihydrate by their X-ray powder diffractograms described in Tables 1 to 3. EXAMPLE 1

15.0 g of erythromycin A oxime hydrochloride (erythromycin A oxime content: 65.3% based on the free base) are suspended in 75 ml of water at 20°. The pH is adjusted to 9.5 by addition of 20% (w/w) aqueous sodium hydroxide within about 15 minutes. The reaction mixture is stirred for 30 minutes keeping the same conditions of pH and temperature. A compound of formula I in free base form crystallizes, the precipitate is filtrated off, washed with 10 ml of water and dried.

10.04 g of erythromycin A oxime in the form of a dihydrate with an oxime content of 94.2 % (what means an oxime content of 99.0% on anhydrous basis) are obtained Water content (Karl Fischer): 4.9 % Yield: 96.6 % of theory.

EXAMPLE 2

Repeating Example 1 , but adjusting a pH of 8.5.0 instead of 9.5; by addition of 25 % aqueous ammonia of 20% (w/w) instead of aqueous sodium hydroxy de; results in crystalline erythromycin A oxime in the form of a dihydrate with an oxime content of 93.5% (what means an oxime content of 98.3 % on anhydrous basis). Water content (Karl Fischer): 4.8 %. Yield: 93.9 % of theory.

EXAMPLE 3

Repeating Example 1 , but using an erythromycin oxime hydrochloride having an eythromycin A oxime content based on the hydrochloride of 67.1% instead of 65.3%; and adding 4 ml of ethyl acetate to the aqueous mixture of erythromycin oxime hydrochloride results in erythromycin A oxime in the form of a dihydrate with an oxime content of 93.6%(what means an oxime content of 98.4% on anhydrous basis). Water content (Karl Fischer): 4.9 %. Yield: 87.5 % of theory.

Claims

1. A compound of formula

in the form of a dihydrate.

2. A compound of formula I according to claim 1 , having a water content of 4% to 6.5%

3. A compound of formula I according to any one of claims 1 to 2 in crystalline form.

4. A compound of formula I according to claim 1 having a X-ray powder diffraction pattern of

Table 1

d (A) I/I₀

9.42 0.77

7.82 0.52

7.67 0.56

5.87 1.00

4.55 0.52

5. A process for the production of a compound of formula I as defined in claim 1 , comprising converting a compound of formula I in the form of a salt into a compound of formula I in free form in water and isolating a compound of formula I in the form of a dihydrate.

6. A process according to claim 5, wherein a compound of formula I having a water content of 4% to 6.5% is produced.

7. Use of a compound of formula I in the form of a dihydrate in the production of a macrolide of the erythromycin type.

8. A process for the production of a macrolide from the erythromycin A type comprising the steps

(i) converting a compound of formula I according to claim 1 in the form of a salt in water into a compound of formula I in the form of a dihydrate (ii) isolating a compound of formula I in the form of a dihydrate

(iii) converting a compound of formula I in the form of a dihydrate into a macrolide from the erythromycin A type.

9. A process for the production of a macrolide of the erythromycin A type comprising converting a compound of formula I in the form of a dihydrate into a macrolide from the erythromycin A type.

10. A process according to any one of claims 8 or 9, wherein the macrolide is roxythromycin, clarithromycin, or azithromycin.