IE45029B1 - Aminoglycosides - Google Patents

Abstract

Process for preparing 2-deoxystyreptamine aminoglycosides, of general formula: ** (Formula) ** in which R1 is a hydrogen atom or a lower alkyl group; R2 is an amino or hydroxyl group; one of the groups R3 and R4 s a hydrogen atom, while the other represents a glycosyl group; and n is 4, 5 or 6; and its pharmaceutically acceptable acid addition salts.

Description

This invention relates to antibacterial agents and is particularly concerned with novel antibacterial 2-deoxy-streptsmine aminoglycosides and with methods for the preparation of such compounds.

According to Patent Specification No. 42452 there are provided novel compounds having the general formula! where / and R represents an amine or hydroxyl groupj * 3 b one of RJ and R represents a hydrogen atom, while the other represents a glycosyl group as hereinafter defined? n is 1, 2 or 3? (I) and their pharmaceutically-acceptable acid addition salts.

When R^ represents a glycosyl group such group is defined as a single hexopyranosyl group containing two or more hydroxyl groups and preferably containing an amino group, for example a 3-aaino-3-deoxy- " D-glucopyranosyl group as found in kanamycin A and B. Mien R represents a grcup such group is glycosyl' a pentofuranosyl group, optionally linked to a further hexo3 pyranosyl group by a further glycosidic linkage. For example, R may be a jp-B-ribofuranosyl group as found in ribostamycin. The term lower alkyl group means a group containing from 1 to 4 CArbon atoms which may be straight or branched chain.

According to the present invention, which is an improvement or modification of the invention the subject of the above-mentioned δ a o s 3 Patent Specification No, 42452 , there effic now pS&vified-novel compounds of the formula (I) wherein n is 4 to 5.

Pharmaceutically acceptable acid addition salt3 of the compounds of the invention are those formed from acids which form non-toxic acid 5 addition salts containing pharmaceutically acceptable anions, such as the hydrochloride, hydrobromide, sulphate, or bisulphate, phosphate or acid phosphate,’acetate, maleate, fumarate, lactate, tartrate, citrate, gluconate, succinate, ρ-toluene sulphonate and carbonate salts.

The compounds of the invention may be prepared by the methods described in the Comniete Specification of tho above-mentioned Satant Specification No 42453 ', for example by reduction of a compound of the formula: --with a reducing agent in a suitable solvent in order to effect reduction of th» amide link at H-l.

Many of the compounds of formula (II) are known compounds previously disclosed, for example l-H-(6-amino-3-hydroxy-hexanoyl) kanamycin A is described in J, Antibiotics, 1974, 27, 851, Other compounds may be prepared by analogous methods to those disclosed therein.

Generally the- rings are each in the chair form, and each of the substituent groups is disposed equatorially with respect to the ring. Furthermore, the glycosidic linkage between tho hexopyranosyl ring and the 2-deoxystreptamine ring is more usually an ^-linkage , with respect - 3 450 33 to the former, particularly when the compounds of formula (II) are derived from naturally-occurring 2-deoxystreptamine aminoglycosides.

: Additionally the ^-hydroxy- -aminoalkyl group at N-l. may exist in the S or R-form or may be present as a mixture of both optical isomers.

The in vitro evaluation of compounds of the invention as antibacterial agents is performed by determining the minimum inhibitory concentration (K.I.C.) of the test compound in a suitable medium at which growth of the particular micro-organism fails to occur. In practice, agar plates, each having incorporated therein the test compound at a particular concentration are inoculated with a standard number of Cells of the test micro-organism and each plate is then incubated for 24 hours at 37°C. The plates are then observed for the presence or absence of the growth of bacteria andthe appropriate M.I.C. value noted. Microorganisms used in such tests have included strains of Escherichia coli, Klebsiella pneumoniae, Proteus mira bills, Pseudomonas aeruginosa.

Staphylococcus aureus and Streptococcus faecal is.

In vivo evaluation is carried out by administering the compounds subcutaneously to mice which are exposed to a strain of Escherichia coli. Each compound is administered at a series of dosage levels to groups of mice and its activity is determined as the level at which it gives 50% protection, against ’the lethal effect of the Escherichia coli organism over a period of 72 hours.

For humah use, the antibacterial compounds of the invention eaft be administered alone, but will generally be administered irt admixture with a pharmaceutical carrier selected with regard to the intended route of administration and standard pharmaceutical practice.

• For example, they may be administered orally in the form Of tablets .containing such excipients as starch or lactose, or in capsules either alone or in admixture with excipients, or in the form of elixirs or .-4suspensions containing flavouring or colouring agents. They may be injected parenterally, for example, intravenously, intramuscularly or subcutaneously. For parenteral administration, they are best used in the form of a sterile aqueous solution which may contain other solutes, for example, enough salts or glucose to make tho solution isotonic.

For administration to human patients, it is expected that the daily dosage level of the antibacterial compounds of the invention will cs comparable: with that of aminoglycoside antibacterial agents currently in use, e.g. from 0.1 to 50 mg/kg (in divided doses) whan administered by the parenteral routes, or from 10 to 100 mg/kg (in divided doses) when administered by the oral route. Thus tablets 01· ' capsules of the compounds can be expected to contain from 0.1 to 1 g of active compound for administration orally up to 4 times a day, while dosage units for parenteral administration will contain from 10 to 5θθ 1» ng. of active compound. The physician in any event will determine the actual dosage which will be most- suitable for an individual patient and it. will vary with ago,, the weight and response of the particular patient The above dosages are exemplary of the average host. There can, of course, be individual cases where higher or lower dosage ranges are SO merited, She following Example describes the preparation of one particular compound according to the invention. Temperatures are , given in °C; Sephadex is a registered trade mark. - 5 1 EXAMPLE l-N-Qs)-2-hydroxy-6~amino-hexanoyl3 kanamycin A dicarbonate .(1.0 g, I.36 ramole) was dissolved in anhydrous trifluoroacetic acid (10 ml) and the solution evaporated to dryness under vacuum to yield a viscous gum, The residue was treated with a 1 molar solution of diborane in tetrahydrofuran (75 nil) under an atmosphere of dry nitrogen, and the resulting solution heated at 50 - 55° for five hours.

Evaporation of the organic solvent under reduced pressure yielded a .taken up 1 gum which was-in 2N hydrochloric acid (10 al). After 10 minutes the 10 solution was basified to pHlO with 5N sodium hydroxide solution and finally taken to pH6 with 2N hydrochloric acid. The solution was then 1 chromatographed on a column of Sephadex GM-25 in the ammonium-ion form (3.5 x 90 cm) eluting with water and a gradient of ammonium hydroxide of increasing concentration from 0 to 0.6N. Fractions containing the product, as monitored by thin layer chromatography were combined and evaporated under vacuum to yield ,1-M-pS)-2-hydroxy-6-amino-hexyl] kanamycin A (0,64 g, 63%)· ...................... f t · Thin layer electrophoresis, Rf = 0.85 • (The electrolyte was an equipart mixture of acetic and t . formic acids, giving a pH value of 2, ahd a potential difference of $00 volts was applied afcross the ends of the 20 cia silica coated plate for 45 minutes. Dete'ction was performed by drying the plate, spraying with a cyclohexane solution of tertiary-butyl hypochlorite and then drying, cooling and developing the plate with starch-potassium iodide solution, tinder these conditions the starting material gave an Rf value of I.O). - 6 Maas spectrometry A sample was converted to the volatile pcnta-H-acetylocta-O-trimethylsilyl derivative by treatment with acetic anhydride in methanol at room temperature for 24 hours foilowed by reaction with η 2ίί mixture of hexamethyldisilazane and trimethylchlorosilane at room temperature for 24 hours. m/e found 1385. C58H 123K3°i7Si8 rGcluirGS % 1.385Results of the testing of the compound of the Example for antibacterial activity in vitro by t’ne methods previously described are giver, in the following Table.

TABLE; In vitro activity r~ B. Coli ~μ Klebsiella j Proteus pneumoniae 1 mirabilis Pseudomonas 1 Staphylococcus aeruginosa aureus

Claims (10)

1. where ro R represents an anjino or hydroxyl group; one of R^ and R^ represents a hydrogen atom, while the other represents a glycosyl group as herein defined; and n is 4, 5 or 6; and their pharmaceutically acceptable acid addition salts.

2. Compounds according to claim 1 in which R is a hydrogen atom and n is 4. .,

3. Compounds according to claim i or 2 in which R is a hydrogen 4. / atom and ft is a 3”araino-3“deoxy-p< -D-glucopyranosyl group.

4. l-N-£(S)-2-hydroxy-6-arainohexyl]kanamycin A.

5. A process for preparing compounds of formula (I) as defined in claim 1 which comprises reducing a compound of the formula: OLNHR 1 / — 0 HO—/ H0 < A r 2 i 4. where R to R and and isolating the compound of formula (I).

6. A process as claimed in claim 3 in which the compound of formuia (II) is seduced with dibdrano to give the compound of formula (X).

7. ' A process as claimed in claim 5 substantially as described in the Example

8. , ^S0S3 A compound of formula (ϊ) as defined in claim 1 which has been prepared by a process as claimed in any one of claims 5 to 7.

9. , Pharmaceutical compositions coa^risisg a compound as claimed in any one of claims 1 to 4 together with a pharmaceutically acceptable carrier.

10. , A method of treating gram-positive and gram-negative bacterial infections in non-human animals which comprises administering to the aa&aul an effective amount of a compound as claimed in any cf claims 1 to 4 either alone or in tho form of a pharmaceutical composition oc claimed in claim 9,