GB2073737A - Rifamycins - Google Patents

Abstract

New rifamycin compounds of the formulae I and II <IMAGE> Y=H or CH3CO; R1 is C1-C7 alkyl or C3-C4 alkenyl, R2 is C1-C7 alkyl, C2-C4 chloroalkyl, C3-C4 alkenyl, Cycloalkyl having 3 to 7 C atoms in the ring, cycloalkyl alkyl having 3 to 6 C atoms in the ring, phenyl, bornyl, or C7-C8 aralkyl, unsubstituted or mono-substituted by a halogen atom in the aryl group; or NR1R2 is a cyclic moiety having 5 to 8 C atoms unsubstituted or substituted by 1 or 2 CH3 group(s), 4-alkyl-1-piperzinyl, morpholino or 1,2,3,4- tetrahydroisoquinolinyl, which inhibit the growth of gram positive bacteria and mycobacterium tuberculosis, are prepared by formation of the imino group.

Description

SPECIFICATION Rifamycins The invention relates to S and SV rifamycin derivatives, to methods for their preparation and to pharmaceutical compositions containing them.

The invention provides rifamycin compounds having the general formula I

wherein Y represents a hydrogen atom or an acetyl group and either R1 represents a linear or branched alkyl group having from 1 to 7 carbon atoms or an alkenyl group having 3 or 4 carbon atoms, and R2 represents a linear or branched alkyl group having from 1 to 7 carbon atoms, a chloroalkyl group having from 2 to 4 carbon atoms, an alkenyl group having 3 or 4 carbon atoms, a cycloalkyl group having from 3 to 7 carbon atoms in the ring, a cycloalkyl alkyl group having from 3 to 6 carbon atoms in the ring, a phenyl or bornyl group, an unsubstituted aralkyl group having 7 or 8 carbon atoms or an aralkyl group having 7 or 8 carbon atoms and substituted by one halogen atom in the aryl group, or R, and R2 together with the nitrogen atom to which they are bonded represent an unsubstituted cyclic moiety having from 5 to 8 carbon atoms, a cyclic moiety having from 5 to 8 carbon atoms substituted by one or two methyl group(s), a 4-alkyl-i -piperazinyl group or a morpholino or 1 ,2,3,4-tetrahydroisoquinolinyl group.

The invention also provides compounds of the general formula II

wherein Y, R1 and R2 are as above defined. These compounds of the general formula II are reduction products of the compounds of the general formula I.

The rifamycin compunds according to the invention have antibacterial activity against Grampositive and Gram-negative bacteria and against Mycobacterium Tuberculosis. The compounds of the general formula I are grey to black solids, while those of the general formula II are orange solids. They are generally soluble in most organic solvents, such as chlorinated solvents, alcohols and esters. The compounds of the general formula I are insoluble in aqueous solutions but soluble in aromatic hydrocarbons, whereas the compounds of the general formula II are slightly soluble in water at a pH of between 7 and 8.

The compounds of the general formula I may be prepared by a process comprising reacting a 3amino-rifomycin S of the general formula III

wherein Y represents a hydrogen atom or an acetyl group, in the presence of a tertiary amine and of an aprotic solvent, with a chloroformiminium chloride of the general formula IV

wherein R1 and R2 are as above defined. This process is within the scope of the invention.

Following the same reaction but using 3-amino rifamycin SV in place of 3-amino rifamycin S, the compounds of the general formula II may be directly obtained. This process is also within the scope of the invention.

The compounds of the general formula Ill are disclosed in German Patent Specification No,1,670,377 and in United States Patent Specification No. 4,007,169. The compounds of the general formula IV are described in British Patent Specification 1,293,590.

The tertiary amine is suitably triethylamine. Several aprotic solvents are suitable, including tetrahydrofuran, dioxan, chloroform, dichloromethane, benzene or toluene.

The compounds of the general formula Il may alternatively be prepared from the corresponding compounds of the general formula I by the reduction with zinc and acetic acid or with ascorbic acid or a salt thereof.

The rifamycin compounds according to the invention may be admixed with a pharmaceutically acceptable carrier or diluent to form a pharmaceutical composition within the scope of the invention.

Whether alone or in such a composition, they may be formulated for administration in conventional unit dosage forms.

The invention is illustrated by the following Examples, in which the carbon atom numbers given in the PMR spectral data have been assigned according to IUPAC rules.

Example 1 3-[( Hexahydro-1 H-azepin-l -yl)-methyleneimino]-rifamycin S 1 6 g of 3-amino-rifamycin S were dissolved in 1 50 ml of chloroform and 2.5 ml of triethylamine were added to the solution. After cooling to -300C, 9.5 g of chlorohexahydroazepinylformiminium chloride dissolved in 1 50 ml of chloroform were added dropwise under stirring. The solution was gently warmed up to 200 C, washed with water and dried on anhydrous sodium sulphate. After filtering the solution, the solvent was evaporated off under reduced pressure, and the residue was dissolved in 100 ml of dichloromethane. The solution was diluted with 300 ml of cyclohexane and then concentrated to 250 ml under reduced pressure.The precipitate was filtered off, the solvent was evaporated off under reduced pressure, the residue was dissolved in 100 ml of diethyl ether, and the solution was diluted with 200 ml of petroleum ether, washed with a phosphate buffer solution at pH 7.5 and then washed with water. The organic phase was dried on anhydrous sodium sulphate, filtered and evaporated to dryness.

Yield: 1.5 g of a compound of the general formula I wherein Y=COCH3 and NR1R2=hexahydroazepinyl.

P.M.R. (CDCI3): 0.43 a [d, CH3-C(22)]; 0.77 â [d, CH3-C(20)]; 0.87 S [d, CH3-C(1 6)]; 1.07 â [d, CH3-C(1 8)]; 1.80 a [s, CH-C(2)]; 2.03 a [s, CH3C00-C(21)]; 2.13 8 [s, CH3-C(1 2)]; 2.30 8 [s, CH3-C(4)j; 3.15 8 [s, CH30-J;

4.5--5.4 S[m, C(21)H and C(24)H]; 5.8--6.8 S [m, C(13)H, C(14)H, C(15)H, C(25)H]; 7.40 6 [bs, NH-CO]; 8.12 8[s, N=CH-N].

MS: 819 (M+).

Example 2 3-(Piperidino-methylenei mino)-rifamycin S 8 g of 3-amino-rifamycin S were dissolved in 100 ml of dichloromethane, 7 ml of triethylamine were added and the solution was cooled to -400C. A solution of 8 g of chloropiperidylformiminium chloride in 50 ml dichloromethane was added dropwise and the temperature was kept at -400C for 60 minutes. the solution was gently warmed up to room temperature, and washed with dilute acetic acid and then with water. After drying on anhydrous sodium sulphate, the solution was evaporated under reduced pressure and the residue was extracted with 400 ml of diethyl ether. The ethereal solution was washed with a phosphate buffer solution at pH 7.5 and then with water.After drying on anhydrous sodium sulphate, the solution was diluted with 100 ml of petroleum ether and then concentrated to 50 ml under reduced pressure. The precipitate was filtered off yielding 2 g of a compound of the general formula I wherein Y=COCH3 and NR1R2=piperidyl.

P.M.R. (CDCl3): 0.43 at [d, CH3C(22)]; 0.68 8 [d, CH3C(20)]; 0.79 8 [d, CH3-C(1 6)]; 0.97 â[d, CH3-C(1 8)]; 1.75 # [s, CH3-C(2]; 1.98 # [s, CH3C00-C(21)]; 2.08 # [s, CH3-C(1 2)]; 2.27# [s, CH3-C(4)]; 3.148 [s, CH3O-];

4.7-5.3 8 [m, C(2 1 )H and C(24)H]; 5.5-6.7 8 [m, C(1 3)H, C(1 4)H, C(1 5)H and C(25)H]; 7.67 8 [bs, NH-CO]; 8.20# [S, N=CH-N].

MS: 805 (M+).

Example 3 3-[( Hexahydrn-1 H-azepin-1 -yl)-methyleneimino]-rifamycin SV 0.250 g of 3-[(hexahydro-1 H-azepin-l -yl)methyleneamino]-rifamycin S, obtained as described in Example 1 were dissolved in 10 ml of methanol and reacted with a solution of 0.5 g of sodium ascorbate in 10 ml of water. After stirring for 20 minutes, 30 ml of dichloromethane were added, the organic phase was washed with water, dried on anhydrous sodium sulphate and filtered. The solvent was evaporated off under reduced pressure, the residue was treated with petroleum ether and the precipitate was filtered off. 0.200 g of a compound of the general formula II were obtained, wherein Y=COCH3 and NR1R2=hexahydroazepinyl.

P.M.R. (CPCla): -0.098 [d, CH3-C(22)]; 0.48# [d, CH3-C(20)]; 0.83 8 [d, CH3--C(16)]; 1.01 8 [d, CH3-C( 18)]; 1.77 8 [s, CH3-C(2)]; 1.97 8 [s,CH3COO-C(21)];2.03 8 [s, CH3-C(12)];2.10# [s, CH3-C(4)]; 3.048 [s, CH3O-];

4.7-5.6 # [m, C(21)H and C(24)H]; 6.0-6.5 8 [m, C(1 3)H, C(1 4)H, C(15)H,C(25)H]; 8.53 8 [s, -N=CH-N < ]; 8.63# [bs, NH-CO].

MS: 821 (M+).

Example 4 3-[(Pyrrol idin-1 -yl)-methyleneimino]-rifamycin SV 8 g of 3-amino-rifamycin S were dissolved in 40 ml of tetrahydrofuran and 10 ml of triethylamine were added. 7.5 g of chloropyrrolidinylformiminium chloride were added at 1 50C. The solution was stirred for 20 minutes at room temperature, 100 ml chloroform were added and the resulting solution was washed with dilute acetic acid and then with water. After drying on anhydrous sodium sulphate, the solution was filtered and evaporated under reduced pressure. The residue was dissolved in 50 ml of methanol and reacted with a solution of 1 g of sodium ascorbate in 20 ml of water. After stirring for 10 minutes, 100 ml of chloroform were added, the organic phase was washed with water, dried on anhydrous sodium sulphate and filtered.The solvent was evaporated off under reduced pressure. The residue was stirred with 200 ml of diethylether for 1 5 minutes. After filtering, the ethereal solution was extracted with a phosphate buffer solution at pH 7.5. The aqueous phase was washed with diethyl ether, acetic acid was added to pH 3.5 and the aqueous solution was extracted with chloroform. The chloroform phase, washed with water and dried on anhydrous sodium sulphate, was filtered and diluted with two volumes of petroleum ether. 0.500 g of an orange compound of the general formula II were obtained, wherein Y=COCH3 and NR1R2=pyrrolidinyl.

P.M.R. (CDCI3): -0.058 [d, CH3-C(22)]; 0.548 [d, CH3-C(20)]; 0.82 8 [d, CH3-C(1 6)]; 1.048 [d, CH3-C(1 8)]; 1.76 8 [s, CH3-C(2)]; 1.97 8 [s, CH3-C00-C(2 1)]; 2.07 8 [s, CH3-C(1 2)j; 2.15 8 [s, CH3-C(4)]; 3.05 8 [s, CH30-];

4.8-5.58 [m, C(21)H and C(24)H]; 6.0-6.58 [m, C(13)H, C(14)H, C(1 5)H, C(25)H]; 8.748 [s, -N=CH-N]; 8.83 8 [bs, -NH-CO-].

MS: 793 (M+).

Example 5 3-[(4methyl-piperazin-I -yl)-methyleneimino]-rifamycin SV Following the procedure described in Example 4 and reacting 3-amino-rifamycin S with chloro (4-methyl-piperazin-1-yl-formiminium chloride a compound of the general formula II was obtained wherein Y=COCH3 and NR1R2=4-methyl-1 -piperazinyl.

MS: 822 (Mt).

The activity in vitro of the rifamycin compound obtained according to Example 4 has been tested by the serial twofold dilution technique in solid medium (Gram+ and Gram- bacteria) or in liquid medium (Mycobacterium tuberculosis).

After incubation at 370C the MICs were recorded as the minimal concentrations able to prevent any visible growth of the test strains.

The results, in comparison with those of Rifampicin, are set out in the following Table, wherein the figures are the values of the minimal inhibiting concentration (MIC) given in mcg/ml.

Table Strains Ex. 4 Rifampicin Staphylococcus aureus 0.0045 0.009 Streptococcus faecalis 1.25 0.3 Streptococcus pyogenes 0.6 0.6 Sarcina lutea 0.0045 0.009 Mycobacterium tuberculosis 0.0025 0.01 Escherichia coli 200 10 Klebsiella pneumoniae 200 5 Proteusvulgaris 2.5 2.5 Pseudomonas aeruginosa 200 10 Salmonella abortivoequina 200 2.5 The compound of Example 4 inhibits the growth of Gram positive bacteria and Mycobacterium tuberculosis at very low concentrations. The inhibitory action against Mycobacterium tuberculosis is noteworthy, since it is 4 times higher than that of Rifampicin. The spectrum of activity of the compound of Example 4 is more limited than that of Rifampicin; in fact some Gram-negative strains are insensitive to the new compound.

Claims (12)

Claims

1. A rifamycin compound having the general formula I or II as herein defined

2. 3-[(Hexahydro- 1 H-azepin- 1 -yl)-methyleneimino]-rifamycin S.

3. 3-(Piperidino-methyleneimino)-rifamycin S.

4. 3-[(Hexahydro- 1 H-azepin- 1 -yl)-methyleneimino]-rifamycin SV.

5. 3-[(Pyrrolidin-l -yl)-methyleneimino]-rifamycin SV.

6. 3-[(4-methyl-piperazin-l -yl)-methyleneimino]-rifamycin SV.

7. A method for the preparation of a rifamycin compound having the general formula I or II as herein defined, the method comprising reacting a 3-amino-rifamycin S of the general formula Ill as herein defined or as corresponding 3-amino-rifamycin SV with a chloroforminiminium chloride of the general formula IV as herein defined in the presence of a tertiary amine and of an aprotic solvent.

8. A method according to claim 7 in which the tertiary amine is triethylamine.

9. A method according to claim 7 or claim 8 in which the aprotic solvent is tetrahydrofuran, dioxan, chloroform, dichloromethane benzene or toluene.

10. A method for the preparation of a rifamycin compound of the general formula II as herein defined, the method comprising preparing a rifamycin compound of the general formula I as herein defined by a method according to any of claims 7 to 9 and reducing the rifamycin compound of the general formula I with zinc and acetic acid, or with ascorbic acid or a salt thereof.

11. A method for the preparation of a rifamycin compound having the general formula I as herein defined, the method being substantially as herein described with reference to Example 1 or Example 2.

12. A method for the preparation of a rifamycin compound having the general formula II as herein defined, the method being substantially as herein described with reference to Examples 1 and 3, Example 4 or Example 5.

1 3. A pharamceutical composition comprising a rifamycin compound according to any of claims 1 to 6 or a rifamycin compound prepared according to any of claims 7 to 12 in admixture with a pharmaceutically acceptable diluent or carrier.