CS202570B2 - Process for preparing aminoglycsidic antibiotics - Google Patents

Abstract

The kanamycin derivatives of formula I, in which R is an amino or hydroxyl group and R<1> is an alkyl group optionally substituted by hydroxyl and/or amino groups, are obtained by alkylation of the compounds of formula II, in which R<2> is H or a benzyl group, R<3> is an acyl-protecting group and R<4> is a hydroxyl group or an NHR<3> group, followed by the removal of the R<3> groups and the benzyl group R<2>, where appropriate. The compounds of formula II are new intermediates which are obtained by acylation of a kanamycin A, B or a 3-N-benzylkanamycin A, protected on all its amino functional groups, followed by the removal of the protecting groups and the intramolecular migration of the acyl group from oxygen to nitrogen. <IMAGE>

Description

The invention relates to a novel process for the production of amtoogilycoside antibiotics via novel intermediates.

In particular, the invention relates to a process for the preparation of 1-N-substituted kanamycin and derivatives thereof and N-protected derivatives of the same type as preferred intermediates.

Examples of 1-N-substituted kanamycin derivatives are disclosed in U.S. Pat. U.S. Patent No. 195,713; other derivatives are known substances, for example 1-N- [4-amino-2-hydroxybutyryl] kanamycin A (BB-K8), disclosed in British Patent No. 1,401,221. In the manufacture of these substances from kanamycin, which is commercially available, it is desirable to protect some or all of the amino groups at a position other than position 1. Substitution can then be performed almost exclusively on the amino group at the 1-position. This also facilitates the isolation of the resulting 1-N-substituted product. Accordingly, the present invention provides a process for producing 1-N-substituted kanamycin derivatives via selectively protected intermediates.

The present invention provides a process for the preparation of aminoglycoside antibiotics of formula (I)

where

R is amino or hydroxyl; and

R ¹ represents an alkyl of 3 to 6 carbon atoms, optionally further substituted by one or more hydroxy or amino groups, characterized in that a compound of formula II is alkylated

where

R ² represents a hydrogen atom or • benzyl,

R ³ represents an acetyl or trifluoroacetyl group and

R ⁴ represents a hydroxyl group or an N 1HR 3 group, wherein

R 3 is as defined above, by reductive alkylation with an appropriate C 3 -C 6 aldehyde in the presence of a reducing agent in an organic solvent inert to the reaction conditions to form. compounds of formula III

(III) where

R @ ¹ to R @ 4 are as defined above, whereupon R @ 3 is removed by hydrolysis and R @ 2 is optionally hydrogenated when it is benzyl and the resulting compound of formula (I) is isolated.

The (C až-C) alkyl groups have a straight or branched chain. The labile protecting group R 3 on the amino group is an acyl group which can be selectively removed from the compound of formula III by conventional means. When R 3 is trifluoroacetyl, this group can be removed by hydrolysis under mild conditions, for example by treatment with dilute ammonium hydroxide, so that the R 1 group is not destroyed. When R3 is acetyl, more vigorous hydrolysis is required to remove this group.

The process for the preparation of the compounds of the formula I is carried out by first alkylating a compound of the formula II in a first step. The reaction can be carried out in a number of known ways. For example, reductive alkylation may be accomplished using the appropriate aldehyde, ketone, or aldehyde derivative, as described, for example, in U.S. Pat. No. 195,714 or by reducing the corresponding acylated derivative, for example diborane. When a compound of formula (II) in which R2 represents a hydrogen atom, the reaction also occurs in the 3-position, but using only a small excess of reagent, the desired 1-N-substituted isomer can be readily separated from a substituted isomer and from a 1,3-di-N-substituted product in a conventional manner, for example by ion exchange chromatography. This separation can be carried out immediately after the first step or, preferably, after removal of the amino protecting group.

The second step of the process according to the invention is the removal of the protecting group R3 on the amino group at the 2 'position, if it is in this position, the amino group is located at the 6' and 3 'positions, and also the benzyl group at 3' -amino groups when the product contains a benzyl group. In some cases, it still carries the amino group itself, and in this case it is desirable to protect the group during the reaction and then remove the protecting group in the last step of the reaction. A variety of known methods can be used to completely remove the amino-protecting groups, depending on the nature of the protecting group used, the reaction medium and also the appearance. to a substituent at the N-1 position. The medium used may be either aqueous or aqueous, moreover, it is usually a different acid or alkaline medium. For example, a benzyl group can be removed by catalytic hydrogenolysis using palladium as a catalyst Some acyl groups can be removed by hydrolysis under weakly basic conditions, for example trifluoroacetyl can be removed by treatment with 1 N ammonium hydroxide at temperature The room for 24 hours, whereas the acetyl group, the benzyl group and the ethoxycarbonyl group require heating in the presence of 5N sodium hydroxide for several hours at a temperature of 60-80 ° C. The resulting product of formula (I) may optionally be purified in conventional manner, for example by crystallization or by chromatography.

· The process according to the invention may be clearly vysvěttit the production of 1-N- [(S) -4-amino-2-hydroxybutyryljkanamycinu A (BB-K8J from 3-N-benzyl-3 ^u, 6'-di-N-trffu <RTI ID = 0.0> R (4-yllk) </RTI> anamycin

A. The acylation is in this case carried out using (S) -4-benzyloxycarbonylamino-2-hydroxybutyric acid N-hydroxysuccinimide ester. The reaction is carried out in an inert organic solvent, for example tetrahydrofuran, by adding a solution of the active ester to the solution of the fenamycin derivative at 0 ° C. The reaction can be monitored by chromatography and a larger amount of active ester can be added if necessary to complete the reaction. The reaction proceeds well at room temperature and it has been found that the acylation is completed in 48 hours under these conditions. The product is isolated by evaporation of the solvent and can be purified by conventional means, for example by crystallization or by chromatography, but it is more convenient to use it for the next step in the crude state.

Removal of the 3 &apos; - .alpha.-N, N-trifluoroacetyl groups is carried out by bydrolysis under basic conditions, which reaction can be carried out by dissolving the product of the first step in 1 N ammonium hydroxide and allowing this solution to stand for several hours. night at room temperature. The benzyl and benzyloxycarbonyl groups are then removed by catalytic hydrogenolysis. This reaction is readily accomplished by dissolution. the product of the preceding step in a suitable solvent, for example a mixture of methanol, water and acetic acid followed by hydrogenation. for example at a pressure of 446 kPa and a temperature of 40 ° C in the presence of palladium catalyst. Under these conditions, the reaction is complete within 14 hours. The product is isolated after filtration by evaporation of the solvent. Purification of the product can be carried out, for example, by ion exchange chromatography to give the final product in pure form.

Same. The process can be carried out starting from 3 ', 6'-di-N-trifluoriacetylkanamycin A. In this case, the 1-N-substituted product is obtained together with 3- An N-substituted derivative and a 1,3-N-disubstituted product. In this case, it is possible to separate the desired 1-N 2 -silane product from the by-products from, for example, ion exchange chromatography, although the yield is lower. Likewise, the starting material can be used as a starting material 2, 3, 6, 6, 6, 7, 7, 6, 7, 7, 7, 9, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12 of the groups, thereby obtaining 1-N-substituted kanamycin B derivatives.

An example of carrying out the process according to the invention can also be the preparation of N - [(S) -4-amino-2-hydroxybutyl] -canamycin A. In this case, the protected kanamycin intermediate of formula II is first alkylated, e.g. alkylation. an aldehyde derivative as described in the description of the invention. patent. · No. 195 714 and then the N-blocking groups are removed and the resulting product isolated. · This means that, for example, using 3-benzyl-6 ~ - [SJ-dihydrOxymethyltetrahydrol-1,3-oxazin-2-one for the reductive · alkyjaci along with 3 ^U, 6 ^{<-di-N-acetyl} kanamycin A is ^t base hydrolysis must be carried out to remove the acetyl groups with hydrogenolysis to remove the benzyl group to give the final product YOTOTE I wherein R · is hydroxy and R 1 is · (S) -4-amino-2'-hydroxybutyl. Reductive. the alkylation may be carried out in a suitable organic solvent, for example dimethylformamide, using sodium borohydride for several hours at 30 ° C. The acetyl group is removed by bydrolysis with 3 N sodium hydroxide at 80 ^° C for 4 hours, and the benzyl group is removed by catalytic hydrogenation at 60 ° C and pressure. 10 ⁵

Pa in · 16 hours. The resulting product is then separated from the 3 N substituted isomer by chromatography.

Compounds of formula II used in the manufacture of compounds of formula. The novel compounds described in U.S. Pat. No. 202,571. These compounds are obtainable. by moving an acyl group. In one embodiment, the acid addition salt of kanamycin A or B or 3-N-benzylcanamycin A is first reacted with an acylating agent in an acidic medium so as to acylate the hydroxyl groups. The alkali acid addition salt of the acylated product is dissolved in an inert organic solvent and neutralized. Under these conditions · . the acyl group is displaced to an amino group having an acyloxy group in a side position on the ring, for example an amino group in position. 6 ‘and 3,, respectively 2 2 popřípadě in the case. kanamycin B. The remaining O-acyl groups were. then. The resulting product is purified, for example, by chromatography.

This process for the preparation of compounds of formula II is particularly effective for the preparation of those compounds in which R 4 is a hydroxyl group and R ³ is a trifluoroacetyl group. . In this case, kanamycin A or 3-N-benzylkanamycin A is dissolved in trifluoroacetic acid and is reacted with the acid anhydride at 0 ° C. The reaction is completed after a few hours at 0 ° C and then the resulting poly ⁽ O-difluoromethyl) -cycloanamycin derivative and its salt with trine ^or acetate can be isolated by evaporation of the solvent in vacuo. The product is dissolved in an inert organic solvent, preferably tetrahydrofuran a. neutralizes with a base, for example sodium or potassium carbonate. It has been found that, under these conditions, it is possible to carry out an O - »shift. N acyl groups. the reaction is terminated in 20 minutes at room temperature. The remaining O-trifluoroacetyl groups. The resulting 3 ', 6'-di-N-trifluoroacetyl derivative can be isolated by evaporation of the solvent and purified by conventional column chromatography.

It is also possible to proceed as follows:. that: s.e. kanamycin A or 3-N-benzylkanamycin is first reacted with a deprotecting agent and an amino group. Suitable groups are, for example. . t-butyloxycarbonyl. or benzyloxycarbnyl.

Ί

The product thus protected is then subjected to O-acylation in a known manner, for example by treatment with an acid anhydride or acid chloride such as acetic acid anhydride in pyridine or with an alkyl chloroformate such as ethyl chloroformate, after which the blocking groups are removed again, for example by t-butyloxycarbonyl the group is removed by treatment with trifluoroacetic acid and the benzyloxycarbonyl group by catalytic hydrogenolysis. The displacement of the O-N α -cyl groups is then carried out as above and the remaining O-acyl groups are removed and the product isolated as described.

The process of the invention may also be carried out using kanamycin B, an acyl group. In this case, it moves from the 3'-hydroxyl group to the adjacent 2'-amino group to form the tri-N-acylated intermediate.

The compounds of formula I prepared by the process of the invention, as well as the compounds of formula II and III, can exist in several forms. Typically, the substituents on the ring may be equatorial to the ring. In addition, the glycosidic bond between the hexopyranosyl ring and the 2-desoxystreptamine ring is usually in the X position.

3-N-benzyllikanamycin A is a novel compound. This material can be obtained by reductive alkylation of kanamycin and treatment with benzaldehyde at a certain pH. It has been found that the alkylation of kanamycin A in an aqueous solution at room temperature or at a lower temperature using excess benzaldehyde in the presence of sodium cyanoborohydride requires that the pH of the solution be maintained at 6. In this case, 3 N benzylcanamycin is the main reaction product. A. As a rule, other N-substituted isomers as well as polysubstituted products are formed as by-products and can be separated by conventional ion exchange chromatography. The main fraction isolated from the ammonium hydroxide elution column is 3-N-benzylcanamycin A together with a small amount of 1-N-benzyl'isomer. For practical purposes, the hot product is sufficiently pure, although the 1N-benzyl isomer will, upon acylation and alkylation, yield the 3-N * substituted isomer together with the desired 1-N-substituted product of formula I. This product can be separated by c-hromatography .

The following Example 1 describes the preparation of 3-N-benzylcanamycin A. Examples 2 to 5 describe the preparation of novel compounds of formula II. Examples 6-9 describe the preparation of novel compounds of formula I.

Chromatography was performed on a thin layer of silica using the solvent system. The blots were developed after drying the plates by spraying · 5% · t-butyl hypochlorite in cyclohexane, drying the plates at ^100? C for 10 · · -minut in a ventilated drying oven, followed by quenching 'spraying with a solution of potassium iodide and starch.

Temperatures are given in degrees Celsius. 'AmbeeHt' is a protected word mark referring to an ion exchange resin made of a polystyrene base cross-linked with 3 to 5% diVinylbenzene and containing sulfonic acid residues introduced by sulfonation.

He did

24.3 g (0.03 то! И) of kanamycin A. in the form of sulfate, it is dissolved in 150 ml of water and the pH is adjusted to 6 by adding 5-N-hydrochloric acid dropwise. 1.95 g of 0.03 mol of sodium cyanoborohydride was added and the mixture was cooled to 0 ° C and stirred, while a solution of 3.61 g (0.33 mol) of benzaldehyde in 15 ml of methane was slowly added over 2.5 hours. The mixture was allowed to warm to room temperature. After 16 hours, the pH of the solution was adjusted to 5.5 by the addition of 1N hydrochloric acid, and the solution was filtered and applied to an ion exchange resin column (Am ^e ^hh-t CG-50) in NH 4 ⁺ -form. The column is eluted with water and then with an increasing amount of ammonia in water, the ammonia concentration increases in the range of 0 'to 0.7 N, thereby obtaining the main product 3-N-ibenzzkanamycin A together with a small amount of 1-N- benzyl derivative, product amount 5.0 g, yield 28% ^o / o, Rf 0.44 in methanol / chloroform / 17% ammonium hydroxide 4: 1: 2. Pure kazamycin A has an Rf value of 0.15.

A sample of the product can be converted to the volatile tetra-Niacetylhepta-O-trimethylsilyl derivative by treatment with acetic anhydride in methanol at room temperature for 24 hours, followed by reaction with a mixture of hexamethylditllazase and trimethylchlorosilase in. 1 at room temperature for 24 hours, m / e for C 54 H 106 N 4 O 10 SS17: calcd. 1246 and found 1246.

The position of tuestitunnt was confirmed by the following sequence of reactions.

(a) treatment with t-eutyloxycarbosyl azide affords a compound containing 3 thiutyloxycarbosyl groups together with a benzyl group as confirmed by NMR spectrum;

b) hydrogenation may remove the benzyl group;

c) acylation can be carried out with N - [(S) -4-enzyloxycarbonylamino-2-hydroxyethyl-butyryl-oxy) succizimide; and

d) The N-protecting group can be removed by hydrogenation followed by treatment with trifluoroacetic acid to give 3-N - [(Si-4-amino-2-hydroxyhydroxyutyl) kazamyciz A (BB-K29) as the main product. ) identical to the sample obtained by the method of Naito-et al. (J. Antibiotics, 1973, 26, 297).

Example 2

5.0 ml of anhydride are slowly added with stirring to a solution of 1.0 g of kanamycin A in 40 ml of trifluoroacetic acid at 0 ° C. The solution was allowed to stand at 0-4 ° C for 20 hours. The solvent was then evaporated in vacuo and the residue was mixed with. 10 ml of toluene and evaporated to dryness. The trifluoroacetate salt is mixed with anhydrous tetrahydrofuran and slowly neutralized by stirring. stirring adds an excess suspension of anhydrous potassium carbonate in tetrahydrofuran. The mixture was stirred at room temperature for 20 minutes and the suspension was then filtered and the filtrate was evaporated to dryness. The product is mixed with 20 ml of methanol and allowed to stand at room temperature for 30 minutes. The solvent was evaporated under reduced pressure and the residue was chromatographed on a silica column ^. eluting with a 3: 1 mixture of chloroform and methanol up to a variable concentration of chloroform, methanol and 17% ammonium hydroxide at a ratio of 8: 4: 1 to give 0.52 g of 3 ', 6'-di- hydrate. N-trifluoromethyl-N-triamethylaminamycin A as a white hygroscopic substance. Rf = 0.7 using a 4: 1 mixture of methanol, chloroform and 17o / ₀ ammonium hydroxide: 1, kanamycin A has an Rf of 0.05 in c = o 1665 cm -1.

A sample of the product was converted to the volatile di-N-α 1 ((ethoxy) -butyl) -1- (4-ethoxy) -silyl derivative according to Example 1. m / e for C 47 H 94 N 4 O 15 F 6 S 17: calculated 1264, found 1264.

Example 3

0.7 ml (5 mmol) of tri-trifluoroacetic anhydride was added slowly to a solution of 0.23 g (0.4 mmol) of 3-N-benzylcyanamycin A in 15 ml of trinuoroacetic acid at 0 ° C. The solution was kept at -40 ^DEG C. for 20 hours. The solvent was evaporated and the residue was treated with 10 ml of toluene and evaporated to dryness. The product was dissolved in 20 ml of tetrahydrofuran and added slowly to a suspension of excess potassium carbonate in tetrahydrofuran with stirring. The suspension was stirred at room temperature for 30 minutes, filtered and the filtrate was evaporated to dryness under reduced pressure. The residue is treated with 20 ml of methanol and allowed to stand at room temperature for 30 minutes. Then the solvent was evaporated in vacuo to give a solid. gives 3-N-benzyl-3 ', 6'-di-N-trifluoroacetylkanamycin A having an Rf of 0.5 using methanol, chloroform and 8% ammonium hydroxide in a ratio of 4: 1: 0.1. 3-N-benzylkanamycin A has an Rf of 0.01.

Ex. k 1 and d 4

A. A solution of 189.4 g, 3.3 ^µ , 6'-tetrat-N-benzyloxycarbonylcanamycin A (Bull. Chem. Soc. Japan, 1965, 38, 1181) in 56.8 ml pyridine and 189 ml acetic anhydride is stirred through The mixture was poured into 1.9 liters of water. The aqueous solution was extracted with chloroform (1 x 1.8 L and 1 x 1.0 L) and the organic extract was evaporated to dryness under reduced pressure. Mixing the residue with ether gave 2,24,8 g of penta-O-acetyl-l, 3,3 ', ^6'-ι tetratNtbenzyloxykarbonyl kanat erythromycin A which · filtered and dried in vacuo. The melting point of the product is 223 (up to 229 ° C, Rf = 0.55 in chloroform, σ = 1.8 to 2.05 (1'5 proton multiplets, 5 acetyl groups) and 7.4 (20 proton singlets, 4). phenyl groups.

B. A solution of 53 g Penta-O-aceΐyl-l, 3,3 ', 6 ^<T tetra-N-benzyloxykarbonylk annamycin A in 260 ml of ethyl acetate content. 260 ml of glacial acetic acid was hydrogenated using 5% palladium on charcoal in a total amount of 15 g at 60 ° C and 446 kPa for 7 hours. The solution is filtered and the filtrate is evaporated to dryness under reduced pressure. The residue was treated with ether and the resulting penta-O-acetylcanamycin (32.9 g) was dried in vacuo. The product has a melting point of 97-105 ° C, Rf 0.0 in a mixture of chloroform and ethanol denatured with methanol in a ratio of 12: 1 compared to an Rf of 0.55 starting material. The total absence of aromatic protons was demonstrated at proton magnetic resonance.

C. A solution of 139.2 g of pentathetyl acetanamycin A in 1.4 L of ammonia saturated methanol was allowed to stand overnight at room temperature and then. Evaporate to dryness under reduced pressure. The residue is dissolved in 140 ml of methanol and the crude product is precipitated with 2.5 l of chloroform, filtered and evaporated in vacuo. The crude product was suspended in 400 ml of technical · · ethanol denatured with methanol, and 91.9 g výsledného- 3 ", 6-TDI ^ζ Ntacetylkanamycinu A is separated by filtration, washed with ether and dried in vacuo. The product melts at 150-180 ⁰¹ C. Rf 0.77 in methanol. The NMR and proton spectra were in full agreement with the proposed structure.

Example 5

3.6 ml. Trifloacetic anhydride is slowly added with stirring to a solution of 960 mg (2 mmol) of kanamycin B in 50 ml of trisodium (III) acid. at 0 ^O! C. Allow the solution to stand at 0 · 4 ° C for 20 hours. The solvent is evaporated off under reduced pressure and the residue is treated with 10 ml of toluene and evaporated to dryness. The trifluoroacetate salt was dissolved in 30 ml of tetrahydrofuran and the solution was slowly added with stirring to an excess of triethylamine in tetrahydrofuran. The solution was allowed to stand for 40 ¹ minute at room temperature, then the solvent was evaporated · under vacuum. The residue was dissolved in methanol to hydrolyze the remaining O-trifluoroacetyl group and after 30 minutes at room temperature the solvent was evaporated under reduced pressure and the product was chromatographed on silica using a chloroform / methanol mixture to elute the column. · in the ratio 3: 1 proportion .stoupajícím ammonium hydroxide until the resulting mixture of chloroform, methanol and 17% ammonium hydroxide in a ratio of 20 · 10: 1 thereby zís202570 ka 4'5'2 mg (29 '%) of 2 ^< , 3 ', ^6'-tri-s-N trifh ^ orc ^ <^ etylkanamycin B as a glassy material. The product (having an Rf of 0.70 in a 4: 1: 0.1 mixture of methanol, chloroform and 8% ammonium hydroxide, kanamycin B had an Rf of 0.0.

The structure of the product was confirmed by the following sequence of reactions:

a) acetylation was performed with acetic anhydride in methanol for 20 hours at room temperature followed by treatment. 1 N ammonium hydroxide for 18 hours to remove the trifluoroacetyl group to give the product containing two acetyl groups, m / e for C22H42N5O12: calcd 568, found 568,

b) treatment with deuterium acetic anhydride in methanol at room temperature for 24 hours followed by reaction with 2: 1 hexamethylhyldisilazane and trimethylchlorosilane at room temperature for 24 hours yielded a volatile tri-N-deuteroacetyl-di-N- acetyl-hexa-O-trimethylsilyl derivative, m / e for C46H86N5O15D9Si: calculated 1134, found 1134. Diacetylation occurred on the 2-desoxystreptamine ring, indicating that the trifluoroacetylation was initially performed in the '2', 3 'positions, and 6 'kanamycin B.

example 6

3 &apos;, 6 ' -di-N-trifluoroacetylkanamycin A, prepared from 1.0. according to Example 2, in 40 ml of tetrahydrofuran was added. in reaction with 1.08 g (3.1 mmol) of N- (S) -4-benzyloxycarbonylamino-2-hydroxybutyryloxysuccinimide at 50 ° C. ml of tetrahydrofuran. The solution was allowed to stand at room temperature for 24 hours and then 0.54 g of the same material was added and the solution was concentrated. maintained at room temperature for an additional 24 hours. Solvent. evaporates in. The residue was dissolved in 1 N ammonium hydroxide and the solution was concentrated. Allow to stand for 20 hours at room temperature. Then the solution is evaporated in vacuo and the residue is mixed with mixture d. of oxane, water and acetic acid in a total amount of 55 ml at a 5: 5: 1 ratio to each other and hydrogenated for 6 hours on 5% palladium on activated carbon at 30 ° C and 446 kPa. The mixture was filtered and the filtrate was evaporated. The residue is chromatographed on an ion-exchange resin (Amberlite CG-50) in N & lt ^{; + &gt;} H4 ^{&lt; + &gt;} form, eluting with increasing ammonium hydroxide from 0 to 0.5 N to give 0.11 g of 1N. - [(S) -4-amino-2'-hydroxybutyryl] kanamycin B (BB-K8) in a yield of 9.2 o / ₀ based on kanamycin A. The sample is identical to that of the pure substance.

Example 7

3-N-benzyl-3 ', 6'-di-N-trifluoroacetylkanamycin A prepared from 0.23 g of 3-N-benzylkanamycin A according to the method of Example 3 se. will state. in reaction with the solution. 0.017 g (0.5 mmol) of N- [(S) -4-b ^ i ^ ^ 5 ^ 1o ^^ ^ _l ^ carbonyl amino-

-2-hyddooyl: ethyryloxy] succinimide in 15 ml of tetrahydrofuran at 0 ° C. The solution was allowed to stand at room temperature for 24 hours. Then. 0.35 g of the active ester in tetrahydrofuran is added and the solution is kept at room temperature for a further 20 hours. The solution was evaporated in vacuo and the residue was mixed with methanol / water / acetic acid (30 ml) at 10: 10 ^; And hydrogenated using palladium on charcoal at 40 ° C / 446 kPa for 13.5 hours. . The suspension is filtered and evaporated. The product was purified by chromatography on an ion-exchange resin (Amberlite CG-50) in NH4 ⁺ form as above to yield 84 mg of N - [(S) -4-amino-2-hydroxybutyryl] kanamycin B (BB-K8). yield 36. %, based on 3-N-benzylaminamycin A. The product is identical to the pure sample.

Example 8 ¹

2 ^', 3', 6'-tri-N-tri.lluoracetylkanamycm B was reacted with N- [(S) -4-benzy.loxykarbonylamino-2-hydroxy butyryl yloxy] succinimide as in Example 6 to give the after removal of the protecting groups and purification, the N - [(S) -4- and mn-2-hydroxy-oxo-kanamycin B (BB-K8) is obtained.

Example 9

A solution of 2.84 g of 3 ', 6'-di-N-acetylkanamycin A and 1.305 g of 3-benzyl-6- (S) -di-hydroxymethyl-tetrahydro-1,3-oxazin-2-one in 28.4 ml of dimethylformamide is treated with Heat at 60 ° C for 1 hour and then cool to 30 ° C. 0.189 g of sodium borohydride was added and the mixture was stirred for an additional hour. 1.0 ml of water was added and the mixture was allowed to stand overnight, after which the solvent was added. evaporate under reduced pressure. The residue is heated with 28.4 ml of a 3 N sodium hydroxide solution at 80 DEG C. for 4 hours, after cooling the pH of the reaction mixture is adjusted to

5.7 with concentrated hydrochloric acid. Crude solution of 1 N (S) -4-benzylamino-2-hydroxybutyl). kanamycin A and 3-N - [(S) -4-benzzlamino-2-hydroxybutyl] -canamycin A is passed through an ion exchange resin column (Amberlit.Crr50) in NH4 ⁺ form, eluting first with water to remove inorganic components and to 0.15 M ammonium hydroxide to isolate the crude aminoglycoside mixture. The desired fractions were evaporated and the residue was dissolved in a 15 ml mixture. methanol, 16 ml of acetic acid and 15 ml of water, and then hydrogenated using 30% palladium on charcoal at 60 ° C and pressure. 514 kPa 16 hours. The solution was filtered and the solvent. is evaporated under reduced pressure. The product is purified by ion exchange chromatography as described above to give 1-N4. (S) -4-amino-2-hydroxybutyl] kanamycin A, the sample of which is identical to that of the pure substance.

Claims (3)

A process for the preparation of aminoglycoside antibiotics of the general formula I wherein R is amino or hydroxyl; and R ¹ represents alkyl of 3-6 carbons, optionally further substituted with at least one hydroxy and / or amino *, characterized by subjecting the alkylated compound of formula II R ³ represents an acetyl or trifluoroacetyl group and R ^{4 is a} hydroxy or N'HR ³ group, wherein R ³ is as hereinbefore defined, by reductive alkylation using the appropriate C 3 -C 6 aldehyde in the presence of a reducing agent in an inert organic solvent under the reaction conditions to form a compound of formula III (un wherein R ² represents hydrogen or benzyl, wherein R ^{@ 1} and R ^{@ 4} are as defined above, whereupon the hydrolysis of the R ^{@ 3} group and optionally the hydrogenation of the R ^{@ 2} group when it is benzyl is removed and the resulting compound of formula I is isolated. 2. A method according to claim 1, characterized in that as starting material a compound of formula II wherein R ³ represents a group or trifluoracelylovou <acetyl "group. 3. A process according to claim 2, wherein 3-N-benzyl-3 ', 6 &apos; -di-N-trifluoroacetylkanamycin, 4,3 &apos;, 6 &apos; -di-N &apos; rifluoroacetylkanamycin A, 2 ', 3', 6'-tri-N-trifluoroacetylcanamycin V or 3 ', 6'-di-N-acetyltylkanamycin A.