WO2004026889A1

WO2004026889A1 - Antibiotic derivatives of erythromycin

Info

Publication number: WO2004026889A1
Application number: PCT/GB2003/004003
Authority: WO
Inventors: Audrey Barber Jill
Original assignee: The University Of Manchester
Priority date: 2002-09-20
Filing date: 2003-09-18
Publication date: 2004-04-01
Also published as: AU2003267572A1

Abstract

Erythromycin derivatives having the formula (II) and 5 including 2' esters thereof, and pharmaceutically acceptable salts thereof (II) in which R1 is hydrogen, and R is a hydroxyl group or hydrogen, said derivatives being in isolated form, are useful as antibacterial agents.

Description

ANTIBIOTIC DERIVATIVES OF ERYTHROMYCIN

This invention relates to antibiotics and in particular to antibiotics based on erythromycin.

The actinomycete Saccharropolyspora erythraea produces erythromycin A (formula I, R = OH, R^x= H) and some of its biosynthetic precursors. Erythromycin A (as such or in the form of the 2 ' ethylsuccinate ester or a salt, such as the stearate salt) has been used in the clinic for the treatment of bacterial infection for many years, in particular for treatment of deep seated infections . However its use is associated with a number of problems. In particular, it is associated with severe gastric disturbance in adults so leading to non-compliance of treatment and even unsuitability of use in the event of extreme disturbance.

Erythromycin B (formula I, R = H, R¹ = H) is a biosynthetic precursor of erythromycin A (formula I, R = OH, R¹ = H) and has similar antibacterial activity to erythromycin A but has not been used as an anti-bacterial agent in the clinic .

I Accordingly there is a requirement for an erythromycin derivative that exhibits reduced incidence of gastric disturbance.

Ager and Sood, Magnetic Resonance in Chemistry, Vol : 25, 948-954 (1987) describe a study aimed at providing the complete, unambiguous assignment of the ¹³C NMR spectrum of Erythromycin A. In the course of the study, a mixture of 8- deuterioethythromycin A and its epimer is said to have been separated from anhydroerythromycin A by flash chromatography. However, the ¹³C NMR data provided are not consistent with this statement.

Mordi et al , J. Med. Chem. , 2000, 43, 467-474 describe a comparative study of the acid-catalysed degradation of clarithromycin and erythromycin B using NMR spectroscopy. In the course of this study, a mixture containing 8- deuterioerythromycin B was formed.

The inventor of the present invention has conceived that 8-deuterioerythromycin derivatives, in isolated form, should provide patients with a novel treatment for bacterial infection that shares the benefits of treatment with an erythromycin, but not the undesirable side-effect profile, in particular the gastric disturbance, which should be at least reduced.

According to the present invention, an erythromycin derivative is provided having the formula II and including 2' esters thereof, or a pharmaceutically acceptable salt thereof,

in which R¹ is hydrogen, and R is a hydroxyl group or hydrogen, said derivative being in isolated (e.g. crystalline) form.

It will be appreciated that formula II represents an erythromycin in one specific stereoisomeric form, and hence that the present invention provides an erythromycin derivative isolated in this specific stereoisomeric form.

The erythromycin derivatives of formula II have the hydrogen atom at the 8-position replaced with deuterium. It will be appreciated that one or more of the other hydrogen atoms in formula II may also be replaced with deuterium.

The 2' ester corresponds with formula II in which R¹ is a pharmaceutically acceptable acyl group derived from esterification of a corresponding carboxylic acid residue (for example a mono- or dicarboxylic acid residue) with the hydroxyl group at the 2' position of erythromycin A or erythromycin B. Thus it will be appreciated that the term "pharmaceutically acceptable acyl group" signifies the acyl residue of a pharmaceutically acceptable carboxylic acid.

The acyl group R¹ may, for example, be selected from groups having the formula -CO - R² in which R² may be a C(l- 10) alkyl group or a substituted alkyl group, an aryl group, or a group having the formula -X-CO-O-R³ in which X is an C(l- 10) alkylene or alkenylene group which may be substituted with one or more alkoxy, hydroxy, carboxy (optionally esterified with C(l-10) alkyl) or halide groups and R³ is hydrogen or a C(l-10) alkyl group.

The term alkyl (and alkoxy) herein, unless otherwise stated, contains 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms .

Particular values of R² when an alkyl group are as methyl, ethyl, 1-propyl, isopropyl, 1-butyl, iso-butyl, tert- butyl , pentyl , hexyl , heptyl, octyl , nonyl and decyl ; preferred values of R² are methyl and ethyl, most preferably methyl .

When R² represents a substituted alkyl group, it may be aralkyl having the formula -(CH₂)_n-aryl where aryl is hereinafter defined and n is an integer having the value 1 to 10, preferably 1 or 2. Examples of aralkyl groups are benzyl, 2-phenylethyl, 2-methyl-2-phenylethyl, 2 , 2-dimethyl- 2-phenylethyl .

When R² represents a substituted alkyl group, it may also be an alkyl group substituted with one or more halogen, hydroxy or alkoxy groups .

Particular values of R² when a halogen substituted alkyl are chloromethyl, fluoromethyl, bromomethyl, 2-chloroethyl, 2-fluoroethyl, 2-bromoethyl, chlorofluoromethyl, l-chloro-2- fluoroethyl, 1-fluoro-2-chloroethyl, 2-chloropropyl, 2- fluoropropyl, 2-bromopropyl and trifluoromethyl . Particular values of R² when a hydroxy substituted alkyl are hydroxymethyl , 2-hydroxyethyl, 2-hydroxypropyl, 3- hydroxypropyl , 2 , 3-dihydroxypropyl . Examples of R² alkoxy substituted alkyl are methoxymethyl , ethoxymethyl , 2- methoxyethyl , 2-ethoxyethyl, 2 -methoxypropyl , 2-ethoxypropyl, 3 -methoxypropyl and 3-ethoxypropyl .

Examples of R² when an aryl group are phenyl, naphthyl, both of which may be mono- or multi-substituted (preferably di- or tri-substituted) with halogen, hydroxy, alkyl, alkoxy (preferably methoxy) ; a preferred aryl group is phenyl, most preferably unsubstituted, and preferred halogens are fluorine, chlorine and bromine.

Particular values of R² when an aryl group are phenyl, 2-, 3-, 4-fluoro, chloro, bromophenyl, 2,3-, 2,4-, 2,5-, 2, 6-dichloro- , difluoro-, dibromo-, chlorofluoro- , chlorobromo- , bromofluoro- , 2,3,4-, 2,3,5-, 2, 3, 6-, 3, 4, 5-, 3,4,6-, 4, 5, 6-trichloro- , trifluoro-, dichlorofluoro- , chlorodifluorophenyl, 2-, 3-, 4-methyl-, ethyl-, 1-propyl-, isopropyl-, 1-butyl-, iso-butyl-, tert-butyl-, 2,3-, 2,4-, 2,5-, 2, 6-dimethyl- , diethyl-, dipropyl-, 2-methyl-3 -ethyl- , 2-methyl-4- ethyl-, 2-methyl-5-ethyl- , 2-methyl-6-ethyl- , 3- methyl-2-ethyl-, 2-ethyl-4-methyl- , 2-ethyl-5-methyl- , 2- ethyl-6-ethyl-, 2,3,4-, 2,3,5-, 2, 3, 6-, 3, 4, 5-, 3,4,6-, 4,5,6- trimethyl-, triethyl-, dimethylethyl- and ethyldimethylphenyl .

When R² represents a group of formula -X-CO-O-R³, X may represent, for example, an (Cl-10) alkylene or alkenylene group which may be substituted with one or more alkoxy, hydroxy or halide groups, such as an (Cl-10) alkylene or alkenylene group, especially an (Cl-10) alkylene group.

Examples of X are -CH₂- and -CH₂-CH₂-, -CH₂-CH₂-CH₂- and -CH=CH- . Preferably X is -CH₂-CH₂-.

Examples of R³ are hydrogen, methyl, ethyl, 1-propyl, isopropyl, 1-butyl, iso-butyl and tert-butyl. Preferred alkyl groups are methyl and ethyl .

Preferred values of R¹ are those where R³ is ethyl, and where X is ethylene. Preferred 2' esters are ethylsuccinates, in particular 8-deuterioerythromycin A 2'- ethylsuccinate, including a pharmaceutically acceptable salt thereof .

Pharmaceutically acceptable salts of the compounds of formula II are salts with acids containing pharmaceutically acceptable anions, for example, hydrochloride, hydrobromide, sulphate, bisulphate, phosphate, acid phosphate, acetate, maleate, fumarate, lactate, tartrate, citrate, stearate, oleate, gluconate and succinate.

Examples of specific compounds of formula II include: 8- deuterioerythromycin A, 8-deuterioerythromycin A stearate, 8- deuterioerythromycin A 2 ' ethylsuccinate, 8- deuterioerythromycin B, and 8-deuterioerythromycin B 2 ' ethylsuccinate .

Without wishing to be bound by theory, it is believed that advantageous properties of the erythromycin derivatives according to the invention are attributable to an isotope effect associated with the deuterium at the C₈ position. In the gastric environment, as mimicked by buffer at pH 2.5, an equilibrium exists between the erythromycin derivative having the formula I (i.e. erythromycin A or erythromycin B) and the corresponding enol ether involving cyclisation in a 6, 9-direction. This is shown in the following diagram in which R = R¹ = H)

I I I

Erythromycin B enol ether IV

If, for example, erythromycin B is dissolved in deuterated buffer at pH 2.5, it has been found that the protium at C₈ of erythromycin is replaced by deuterium. This is due to participation of the C₈ proton in the enolisation cyclisation step in the above equilibrium. The following table provides kinetic data relating to the above equilibrium (Mordi et al J. Med. Chem. , 2000, 467-474) :-

Table 1 Kinetic data for Erythromycin B at 37 °C at apparent pH 2.5

The results given in Table I indicate that the equilibrium between erythromycin B and its enol ether shows considerable shift in the equilibrium towards erythromycin rather than its enol ether when deuterium is present at the C₈ position rather than proton. If the source of gastric disturbance with medicines based on erythromycin is caused by the presence of the enol ether, (see Tsuzuki et al ; Chem. Pharm. Bull, 37 (10), 2687-2700 (1989)) then this stable isotope effect explains how the C₈ deuteriated forms of erythromycin A and erythromycin B would be associated with diminished gastric disturbance and hence improved patient compliance.

The C₈ deuteriated erythromycin derivatives of the present invention may therefore be used as a replacement for the derivatives of erythromycin A currently used in the clinic. They may be used for treating bacterial infection by administering to a patient in need of such treatment an effective amount of the derivative. They may be used in amount up to 2g per day, such as 100-1000 mg, typically 250- 500 mg, and pharmaceutical compositions containing an erythromycin derivative having the formula II and including 2' esters thereof, and pharmaceutically acceptable salts thereof are comprehended within the present invention. Therefore, in accordance with this aspect of the present invention there are provided pharmaceutical compositions containing at least 1% by weight of at least one erythromycin derivative having the formula II, desirably at least 50% by weight, preferably at least 75 % and most preferably at least 90%, based on the total weight of antibiotic (deuteriated and non-deuteriated) in the formulation. A suitable pharmaceutical formulation may contain an erythromycin derivative having the formula II or the 2' esters of the invention as the only antibiotic present .

According to another aspect therefore, the present invention provides a pharmaceutical composition comprising a compound of formula II, a pharmaceutically acceptable 2' ester thereof, or a pharmaceutically acceptable salt of said compound or said ester, together with a pharmaceutically acceptable carrier.

C₈-deuteriated Erythromycin A derivative of the invention is preferably administered as a tablet or capsule, preferably enteric coated, or as an injection; C₈-deuteriated Erythromycin B derivative of the invention is preferably administered by tablet, capsule or injection. The 2' esters of C₈-deuteriated Erythromycin A derivative and C₈-deuteriated Erythromycin B are preferably administered orally and hence may be formulated as tablet, capsule, suspension, bolus, and indeed in any formation known in the art of oral administration of medicines, and such; they can be formulated with acidic flavourings and ingredients such as for example, citrus fruits juices or extracts, preferably lemon. Furthermore, a method of treating bacterial infection in a warm blooded animal is provided which comprises administering an effective dose of at least one erythromycin derivative having the formula II and including 2' esters thereof, and pharmaceutically acceptable salts thereof.

The warm blooded animal may be a human or non-human animal .

Also provided is the use of at least one erythromycin derivative in isolated form having the formula II and including 2' esters thereof in the manufacture of a medicament for the treatment of bacterial infection.

The erythromycin derivatives according to the invention may be prepared by a process which comprises treating an enol ether of formula

or a 2 ' ester thereof, with D₂0 in the presence of an acid, followed, if desired, by one or more of the following steps:

(i) for a 2' ester, esterifying an erythromycin derivative of formula II; (ii) for a pharmaceutically acceptable salt, reacting an erythromycin derivative of formula II or a 2' ester thereof with a pharmaceutically acceptable acid;

(iii) for an erythromycin of formula II in which R represents OH, treating an erythromycin derivative of formula II in which R represents hydrogen with Erythromycin C-12 Hydroxylase;

and recovering the erythromycin derivative in isolated form.

Erythromycin derivatives of the present invention may thus be made as shown in the following scheme :-

In accordance with a further aspect of the present invention a process is provided for the manufacture of an erythromycin derivative in isolated form having the formula II in which R is hydrogen or hydroxyl and being deuteriated in the 8-position and including 2' esters thereof which comprises the steps of (i) preparing the corresponding enol ether by treatment of the erythromycin with glacial acetic acid (ii) treating the enol ether with D₂0 at an appropriately acid, preferably buffered, pH and (iii) isolating the erythromycin derivative. Where R is hydrogen (erythromycin B) , the deuteriated derivative is appropriately prepared in a deuteriated aqueous acid solution, for example, a Britton- Robinson buffer, preferably at pH 4 ± 2.5, most preferably at pH 2.3 ± 0.3, and at temperatures at which the reaction mixture is liquid, preferably between 0°C and 50°C, most preferably between 30°C to 40°C. The temperature range and chosen pH are essentially compromises between rate of reaction which is higher at higher temperature and lower pH, and production of side products which also increases with temperature and acidity with resultant difficulty of separating the desired deuteriated erythromycin. These deuteriated erythromycins may be esterified at the 2' position by treatment with an appropriate acid chloride, for example, acetyl chloride, succinyl chloride half ester, before the isolation step (iii) .

Alternatively, erythromycin A or erythromycin B may be esterified at the 2' position before deuteriation, in which situation reaction with acid chloride in the above scheme is not required.

A deuteriated erythromycin B derivative may be converted into a corresponding deuteriated erythromycin A derivative by the action of Erythromycin C-12 Hydroxylase (the product of the Saccharopolyspora erythrraea EryK gene) (D. Stassi, S. Donadio, MJ Staver and L Katz, 1993, J. Bacteriol . 175, 182- 189) . The gene may be expressed in E. coll (RH La balot, DE Cane, JJ Aparicio and L Katz, 1995, Biochemistry, 34, 1858- 1866) where the enzymic product forms in inclusion bodies. After reconstitution (as fully described in the paper) , the enzyme is incubated with a 95-fold molar excess of deuteriated erythromycin B and appropriate cofactors (as described) at 30 °C. After 11 hours, deuteriated erythromycin A is isolated by hplc .

Pharmaceutically acceptable salts may be prepared by methods analogous to methods known for preparing pharmaceutically acceptable salts of erythromycins, for example as described for the preparation of erythromycin A stearate in Polish patent application number P1980-227281.

The erythromycin derivatives of the present invention may be used for the treatment of a wide range of bacterial infections. Examples include tuberculosis, syphilis and chlamydia, lower respiratory tract infections (for example, bronchitis and pneumonia), ear infections, and in particular, skin infections. They may alternatively or additionally be used for the treatment of any condition for which a penicillin would normally be employed and in particular for the treatment of penicillin sensitive patients.

The erythromycin derivatives are particularly useful in situations where gut motility is likely to prove problematic in the long term. They are especially indicated when a patient is expected to consume more than 5 normal courses of erythromycin (normally 35 g) over a lifetime, or when a patient is at particular risk of developing gastro-intestinal disturbance. Examples include patients with penicillin- sensitivity, patients with heart conditions who require prophylactic antibiotics during dental treatment, patients suffering from tuberculosis, patients suffering from kidney infections where erythromycin is indicated, patients suffering from deep-seated or recurrent sexually-transmitted disease (including pelvic inflammatory diease) , immuno- suppressed patients, patients over 60 years old, patients with cancer (the symptoms of a cancer in the brain are similar to those of gastro-intestinal disturbance following erythromycin; where erythromycin is unequivocally indicated in a cancer patient, these drugs are expected to be particularly advantageous) .

The invention is illustrated with reference to the following examples .

Example 1

The preparation and isolation of erythromycin B enol ether

Erythromycin B (200 mg) was dissolved in glacial acetic acid (5 ml) and allowed to stand at room temperature for 4 hours. Saturated sodium bicarbonate solution (50 ml) was added and the enol ether was extracted using dichloromethane (3 x 100 ml) . The organic layer was concentrated under reduced pressure, washed with saturated sodium bicarbonate solution and dried over anhydrous sodium sulphate. The solvent was removed in vacuo, and the colourless crystalline product recrystallised from acetone to give erythromycin B enol ether (177 mg, 91%, m.p. 128-130°C[P Kurath, P H Jones, R S Eganand T J Perun, 1971, Experientia, 27, 362. 126-130°C] M/z700 (M+Z+) ) .

The preparation and isolation of 8-deuterioerythromycin B

Erythromycin B enol ether (100 mg) is added to deuteriated Britton-Robinson buffer at apparent pH 2.5 (10 ml) . The resulting solution is stirred at 37 °C for 15 mins, then cooled to room temperature. The solution is neutralized using 10% sodium hydroxide solution and then extracted using dichloromethane (3 x 20 ml) . The combined organic layers are washed with saturated brine, and dried over anhydrous sodium sulphate. The solvent is removed in vacuo and the colourless crystalline product recrystallised from hexane to give 8- deuterioerythromycin B.

8-deuterioerythromycin B may be esterified at the 2' position using the appropriate acid chloride by literature methods . Example 2

The preparation and isolation of 8-deuterioerythromycin B

Erythromycin B enol ether (1.5g) was dissolved in D₂0 (35 ml) and the pH adjusted to apparent pH 2.3 (deuteriated Britton-Robinson buffer) . The solution was stirred at room temperature for 3 hours and the progress of the reaction was monitored by 1H NMR spectroscopy at 30-minute intervals. The pH of the reaction was measured prior to acquiring each spectrum and necessary adjustments were made using 5% DC1 / NaOD. Figure 1 is a ^XH NMR spectrum at 300MHz at high field of erythromycin B in CDC1₃ in which the doublet representing CH₃-at C19 is shown by an arrow; Figure 2 is a ^"H nmr spectrum at 300MHz of erythromycin B in CDC1₃ in which the signal representing H-8 is shown by an arrow. The reaction was judged to be complete when the ^aH NMR spectrum signal due to CH₃-19 of the enol ether at approx δ 1.6 disappeared (Figure 3 is an NMR spectrum in which a signal from any H-8 is clearly absent at a position shown by an arrow) . The reaction was quenched by adding 5% NaOD solution until the pH of the solution was 8.5 (apparent). 8D-Erythromycin B was isolated by extracting the precipitated solid using 3 x 100 ml dichloromethane. The organic layers were combined and dried over anhydrous sodium sulphate. The organic layer was reduced to dryness using a rotary vapour apparatus and recrystallised from acetone. Yield 65 %; M.p. 203-204° C (198° C for erythromycin B, Wiley et al . (1957) J. Am. Chem . Soc . , 79, 6070-6074); M/z 719 (M+H⁺) 100%.

Figure 4 is the NMR spectrum of 8D-erythromycin B which shows as arrow the singlet due to CH₃-19, further evidence that deuterium has been incorporated into C8. Example 3

The preparation and isolation of 8-deuterioerythromycin A

D-erythromycin B is converted to deuterioerythromycin A by the action of the Erythromycin C-12 Hydroxylase (the product of the Saccharopolyspora erythrraea EryK gene) (D. Stassi, S. Donadio, MJ Staver and L Katz, 1993, J. Bacteriol . 175, 182-189) . The gene may be expressed in E. coll (RH Lambalot, DE Cane, JJ Aparicio and L Katz, 1995, Biochemistry, 34, 1858-1866) where the enzymic product forms in inclusion bodies. After reconstitution (as fully described in the paper) , the enzyme is incubated with a 95- fold molar excess of deuterioerythromycin B and appropriate cofactors (as described) at 30 °C. After 11 hours, deuterioerythromycin A is isolated by hplc.

8-deuterioerythromycin A may be esterified at the 2' position using the appropriate acid chloride by literature methods .

Example 4

Synthesis of 8-D-erythromycin B 2' -ethyl succinate

First Method - Esterification of 8-D-erythromycin B

To a solution of 8-D-erythromycin B (500 mg) in 15 ml acetone, 1 g of sodium bicarbonate (NaHC0₃) (GPR grade, BDH, UK) was added, followed 0.15 ml ethyl succinyl chloride (Lancaster, UK) . The reaction mixture was kept covered and was stirred overnight at room temperature. The volume of the reaction mixture was reduced to 2-3 ml In vacuo using a rotary evaporator (Buchi, Switzerland) . Phosphate buffer (100 mM, pH 6.5) was added and the mixture was stirred for 30 minutes. The white residue was collected using a Buchner funnel, and dissolved in 50 ml of chloroform. The chloroform solution was washed with water and then with saturated brine then dried over anhydrous Na₂S0₄ and reduced to dryness in vacuo . The title compound was recrystallised from acetone. Yield 76.9%, m.p. 96-97° C, ^ NMR (CDC1₃, 500MHz) : δ 0.87 (CH₃-15, t, J = 7.4 Hz), δ 0.96 (CH₃-21, d, J = 7.48 Hz), δ 0.99 (CH₃-2O, d, J = 6.84 Hz), δ 1.14 (CH₃-19, s) , δ 1.19 (CH₃-I7, d, J = 7.3 Hz), δ 1.22 (CH3-6¹, d, J = 6.0 Hz), δ 1.26 (CH₃-7", s), δ 1.27 (CH₃-6", d, J = 6.2 Hz), δ 1.28 (CH₃- 16, d, J^" = 7.05 Hz), δ 1.44 (CH3-I8, s) , δ 2.23 (N(CH₃)₂- 7',8', s), δ 2.86 (CH-2, dq, J^" = 14.56, 7.27 Hz), δ 3.35

(OCH3-8", s), δ 3.49 (CH-5¹, m) , δ 3.52 (CH-5, d, <J = 7.5 Hz), δ 3.76 (CH-11, d, 10.04 Hz), δ 3.98 (CH-5", dq, J^" = 12.40, 6.2 Hz), δ 3.99 (CH-3, dd, J^" = 8.76, 1.5 Hz), δ 4.56 (CH-1¹, d, J = 7.5 Hz), δ 4.74 (CH-2', dd, J= 10.47, 7.48 Hz), δ 4.89 (CH-1", d, J = 4.7 Hz), δ 5.34 (CH-13, dd, J = 9.4, 4.06 Hz), m/z 847 [M+H]⁺, R_f 0.51 (EtOAc: CH₃OH: 25% NH₃ , 85:10:5), Anal . Calcd for C₄₃H₇₄DNOi₅ : C 60.95, H 8.82, N 1.65. Found: C 60.92, H 8.75, N 1.71.

Second Method - Acid-catalysed Hydration of Erythromycin B enol ether 2" -ethyl succinate

A solution of 500 mg erythromycin B enol ether 2' ethyl succinate (WO 00/78772) in 50 ml deuterated Britton-Robinson buffer (apparent pH 2.5) was stirred at ambient temperature and the progress of the reaction monitored by NMR spectroscopy. On completion, the reaction was quenched by adjusting the pH to 8.5, using sodium deuteroxide solution. The aqueous solution was extracted with 3 x 25 ml dichloromethane (GPR grade, BDH, UK) , the organic layers combined, washed with brine and finally dried over anhydrous Na₂S0₄. The organic layer was reduced to dryness in vacuo . The white amorphous solids were recrystallised from acetone to give 0.177 g of the title compound. Yield 35.4%, m.p. 95-97° C, m/z 847 [M+H]\ R_f 0.53 (EtOAc: CH₃OH : 25% NH₃ , 85:10:5). The 1D-^XH NMR spectrum was identical to that of the material synthesised by the First Method.

Example 5 Synthesis of 8-D-erythromycin A 2 '-ethyl succinate

The title compound is prepared following the First Method or the Second Method of Example 4, but using 8-D-erythromycin A as the starting material.

Example 6

Synthesis of 8-D-erythromycin A stearate

Stearic acid (lOOg) is suspended in acetone (200 mL) , and 8- D-erythromycin A (200 g) is added in portions at 45°C.

Activated carbon (1 g) and kieselguhr (diatomaceous earth, 3 g) are then added, and the reaction mixture is heated for 20 minutes at 50-52°C. The reaction mixture is then filtered and mixed with 60 mL deionized water containing acetic acid (0.05 mL) and Tween 80 (0.01 mL) at 40-42° C. After 0.5 h initial crystallisation, a mixture of water (1600 mL) , acetone (100 mL) , and Tween 80 (0.03 mL) is added, and crystallisation is continued for 5 h at 40-41°C. The product is separated by filtration, rinsed with deionized water, and dried at 30-40°C.

Claims

1. An erythromycin derivative having the formula II and including 2' esters thereof, and pharmaceutically acceptable salts thereof

in which R¹ is hydrogen, and R is a hydroxyl group or hydrogen, said derivative being in isolated form.

2. An erythromycin derivative as claimed in Claim 1 in which R¹ is hydrogen, and R is a hydroxyl group.

3. An erythromycin derivative as claimed in Claim 1 in which R and R¹ are both hydrogen.

4. An erythromycin derivative as claimed in claim 1 in which the 2' ester is a compound of formula II in which R¹ is an acyl group that has the formula -CO - R² in which R² may be a C(l-10) alkyl group or a substituted alkyl group, an aryl group, or a group having the formula -X-CO-O-R³ in which X is an C(l-10) alkylene or alkenylene group which may be substituted with one or more alkoxy, hydroxy, carboxy (optionally esterified with C (1-10) alkyl) or halide groups and R³ is a C(l-10) alkyl group.

5. An erythromycin derivative as claimed in claim 4 in which R² may be a C(i-io) alkyl group, an aralkyl group having the formula -(CH₂)_n-aryl wherein n is an integer having the value 1 to 10, or a group having the formula -X-CO-O-R³ in which X is an C (1-10) alkylene or alkenylene group which may be substituted with one or more alkoxy, hydroxy or halide groups .

6. An erythromycin derivative as claimed in claim 4 in which the acyl group R¹ has the formula -CO - R² in which R² is a group having the formula -X-CO-O-R³ in which X is an C(l- 10) alkylene group and R³ is a C(l-10) alkyl group.

7. An erythromycin derivative as claimed in claim 4 in which R² is a group having the formula -X-CO-O-R³ in which X is a group having the formula -CH₂-, -CH₂-CH₂-, -CH₂-CH₂-CH₂- or -CH=CH- .

8. An erythromycin derivative as claimed in Claim 4 in which R³ is ethyl and X is ethylene.

9. An erythromycin derivative as claimed in Claim 1, which is selected from 8-deuterioerythromycin A, 8- deuterioerythromycin A stearate, 8-deuterioerythromycin A 2 ' ethylsuccinate, 8-deuterioerythromycin B, and 8- deuterioerythromycin B 2 ' ethylsuccinate.

10. An erythromycin derivative as claimed in any one of Claims 1 to 9, which is in crystalline form.

11. A pharmaceutical composition, which comprises an erythromycin derivative as claimed in any one of claims 1 to 10 and a pharmaceutically acceptable carrier.

12. A pharmaceutical composition as claimed in Claim 11, which is adapted for oral administration.

5 13. A pharmaceutical composition as claimed in Claim 11 in which the erythromycin derivative is C₈-deuteriated erythromycin A or erythromycin B, the composition being for administration as a tablet or as an injection.

10 14. A pharmaceutical composition as claimed in claim 13 in which the tablet is enteric coated.

15. A pharmaceutical composition as claimed in Claim 11 in which the erythromycin derivative is a 2 'ester of C₈-

15 deuteriated Erythromycin A or erythromycin B, the composition being for administration orally.

16. A pharmaceutical composition as claimed in claim 15 in which the composition for oral administration is in the form

20 of tablet, suspension, or bolus.

17. A method of treating bacterial infection in a warm blooded animal which comprises administering to said animal an effective amount of an erythromycin derivative as claimed

25 in Claim 1.

18. A method as claimed in Claim 17, in which the erythromycin derivative is administered orally and the warm blooded animal is a human deemed at risk of suffering from

30 gastric disturbance if treated with a corresponding non- deuteriated erythromycin derivative.

19. A method as claimed in Claim 18, in which the human is a patient with penicillin-sensitivity, a patient with a heart condition who requires prophylactic antibiotics during dental treatment, a patient suffering from tuberculosis, a patient suffering from a kidney infection where erythromycin is indicated, a patient suffering from a deep-seated or recurrent sexually-transmitted disease, a immuno-suppressed patient, a patient over 60 years old, or a patient with cancer.

20. The use of at least one erythromycin derivative as claimed in any one of Claims 1 to 10 in the manufacture of a medicament for the treatment of bacterial infection.

21. Use as claimed in Claim 20, in which the medicament is an oral medicament and is for the treatment of bacterial infection in a human deemed at risk of suffering from gastric disturbance if treated with the corresponding non-deuteriated erythromycin derivative.

22. A process for the preparation of an erythromycin derivative as claimed in any one of Claims 1 to 10, which comprises treating an enol ether of formula

or a 2 ' ester thereof, with D₂0 in the presence of an acid, followed, if desired, by one or more of the following steps (i) for a 2' ester, esterifying an erythromycin derivative of formula II;

(ii) for a pharmaceutically acceptable salt, reacting an 5 erythromycin derivative of formula II or a 2' ester thereof with a pharmaceutically acceptable acid;

(iii) for an erythromycin of formula II in which R represents OH, treating an erythromycin derivative of formula II in 10 which R represents hydrogen with Erythromycin C-12 Hydroxylase;

and recovering the erythroycin derivative in isolated form.

15 23. A process as claimed in claim 22, in which the erythromycin derivative is recovered by crystallisation.

24. A kit, which comprises an oral pharmaceutical composition as claimed in Claim 12, packaging and 20 instructions for use of the pharmaceutical as an antibacterial agent in the treatment of patients susceptible to gastro-intestinal disturbance.