KR900007318B1 - Method for preparing 4'-epidoxorubicin - Google Patents

Abstract

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Description

Method for preparing 4'-epidoxorubicin

The present invention relates to a novel chemical synthesis method of 4 'epidoxorubicin of formula (V) which is an anti-tumor compound.

4′-Epidoxorubicin is a known anti-tumor compound whose preparation has already been claimed in US Pat. No. 4,058,519 (November 15, 1977). This compound is prepared by condensing adriamycinone with an appropriate reactive sugar derivative, where the reactive sugar derivative obtained by the cumbersome multistep method results in a significant decrease in the final product yield.

It is noteworthy that the sugar derivatives used were prepared by using natural daunosamine as a starting material obtained by dividing glycoside daunorubicin in an acidic medium as obtained by the fermentation method (US Pat. No. 4,012,284). .

In an improved process, the starting material is daunomycin itself, and several chemical reaction steps are carried out on all glycoside structures of the molecule to obtain the desired final product.

By the same improvement methods fully described in the examples herein, the desired product can finally be obtained.

In addition, the simplicity and ease of the required chemical steps essentially affects the overall yield, resulting in 40-50% calculated on the basis of the starting material N-trifluoroacetyl-daunorubicin rather than the yield obtained by the already claimed method. Higher.

This process proceeds through the novel intermediate 4′-keto-N-protected daunorubicin (II), which forms part of the present invention. According to the method of the present invention shown below, N-trifluoroacetyl protected daunorubicin (I) is converted to 4'-epidoxorubicin.

More specifically, it is necessary to protect the amino group of the sugar moiety with an appropriate protecting group in order to carry out the oxidation of the hydroxyl group at C-4 'of daunorubicin: wherein the appropriate protecting group is a trifluoro acetyl group. Use

N-protected daunorubicin (I) is oxidized with activated dimethylsulfoxide (K. Omura and D. Swern. Tetrahedron 1978.34, 1651-1660).

Ketone (II) is obtained in high yield using a bulk base, 1.5-diazocyclo (4.3.0) non-5-ene (DBN), in the basification step of the oxidation reaction.

Selective and stereospecific reduction of the carbonyl functional group in the sugar portion of ketone (II) affords N-protected glycoside (III) with L-arabinoordination. Hydrolysis of the N-protecting group to give glycoside (IV) which is isolated as hydrochloride, followed by bromine to obtain its 14-bromo derivative which is reacted with aqueous sodium formate solution to separate as its hydrochloride To obtain 4′-epidoxorubicin (V).

The starting materials for this process were prepared by reacting daunomycin with trifluoroacetyl anhydride in the presence of an organic solvent, as described in US Pat. No. 3,803,124, and then hydrolyzing the 0-trifluoroacetyl group with methinol. It is a known N-trifluoroacetyldaunomycin (I) which can be easily prepared.

Oxidation of the free hydroxyl group at position C-4 ′ of compound (I) is carried out with DMSO activated by trifluoroacetic anhydride. The reagent is prepared in anhydrous methylene chloride suitably cooled to -50 ° C to -70 ° C. Substrate (I) dissolved in anhydrous methylene chloride is added to the suspension of the reagents while maintaining the temperature at -65 ° C to form the dimethyl alkoxy sulfonium salt. The formation of this salt can be examined by thin layer chromatography: starting material disappears completely after about 30 minutes. Bulk base 1.5-diazo-bicyclo (4.3.0) non-5-ene (DBN) was then added quickly to the reaction mixture maintained at -65 ° C. Once the addition of base is complete (1 '), the reaction mixture is neutralized with acetic acid and poured into methylene chloride to neutralize the reaction: the solution is then washed with water, diluted aqueous sodium bicarbonate solution and water.

The solvent is evaporated and dried to give crude catonone (II), which is purified by chromatography on a column of silicic acid.

The reduction step is carried out in an organic solvent that can be miscible with water such as methanol or dioxane,

Perform with NaBH ₄ while cooling to −10 ° C. for 10 minutes.

Under these conditions, it is desirable to minimize the reduction of carbonyl groups in the side chains of the chromophores and to attach the hydride ions laterally to obtain the corresponding glycosides having hydroxyl groups in the horizontal direction at C-4 '. . Upon completion of the reduction reaction, the reaction mixture is diluted with methylene chloride and washed sequentially with water, diluted hydrochloric acid, water, diluted sodium bicarbonate and water. The solvent is evaporated to afford crude product (III).

The weakly alkaline treatment then removes the N-trifluoroacetyl group from the crude product (III) to give a free glycoside base, which is treated with methanolic hydrochloric acid to separate as its hydrochloride (IV). Treatment of (IV) with bromine affords a 14-bromo derivative followed by hydrolysis with aqueous sodium formate solution to afford 4'-epidoxorubicin (V), which is isolated as its hydrochloride.

Example 1

4'-keto-N-trifluoroacetyl daunorubicin (II)

A solution of 4 ml trifluoroacetic anhydride in 10 ml of anhydrous methylene chloride is added over 15 minutes to a mixture of 60 ml of methylene chloride and 5 ml of anhydrous dimethyl-sulfoxide cooled down to -60 ° C. White precipitates form during the addition. After 15 minutes at −60 ° C., a solution of 6.25 g trifluoroacetyl daunorubicin (I) in 40 ml of methylene chloride is added dropwise to the mixture at −60 ° C. over 15 minutes. The reaction mixture is stirred at −60 ° C. for 30 minutes and is treated rapidly with 9 ml of 1.5-diazocyclo (4.3.0) non-5-ene (DBN) while maintaining the temperature at −60 ° C. After 1 minute the reaction mixture is neutralized with stoichiometric acetic acid and then poured into 300 ml methylene chloride. The organic phase is washed with aqueous 0.1N hydrochloric acid, aqueous sodium bicarbonate solution and water. The organic solution dried over anhydrous sodium sulfate was evaporated to dryness to afford crude product (II), which was purified by chromatography on a column with silica gel using a chloroform-acetone (98: 2 V / V) mixture as eluent. Obtained product (II) (yield 77%): FDMS [M < + >]: 621: PMR (CDCl ₃ ): 1.37 (d, CH ₃ -C-5 '), 2.38 (S, CH ₃ CO), 3.95 (S, CH ₃ O), 4.78 (broad q, C-5'-H), 5.20 (broad S, C-7-H), 5.58 (broad S, C-1'-H), 12.93 and 13.83δ (S, Phenolic Protons)

Example 2

4 ¹ -Epiudaunorubicin HCl (IV)

1.5 g of compound (II) solution in 150 ml of methanol is cooled to -10 ° C and treated with 0.035 g of NaBH ₄ dissolved in 5 ml of methanol. After 10 minutes reduction is complete, the reaction mixture is neutralized with 0.1 N hydrochloric acid and evaporated in vacuo to a small amount (30 ml) and diluted with 200 ml of methylene chloride. The organic solution washed with water is dried over sodium sulfate, evaporated and dried. Crude crude 4 ¹ -Epi-N-trifluoro acetyldaunorubicin (III) is dissolved in 50 ml of 0.1N aqueous sodium hydroxide solution. The resulting solution was left at 5 ° C. for 30 minutes, treated with 0.1N hydrochloric acid to adjust the pH to 4.5 and extracted with chloroform to remove aglycone. The pH of the aqueous solution is then adjusted to 8.6 and repeated extraction with chloroform. The combined extracts were dried over anhydrous sodium sulfate and concentrated to a small volume, acidified with 0.1 N methanolic hydrochloric acid to pH 4.5 to crystallize 1.3 g (yield 87%) of 4 ¹ -epidaunorubicin hydrochloride (IV). do. Melting point 199 to 201 ° C., [α] _D + 320 ° (C 0.045, MeOH)

Example 3

4'-epi-doxorubicin HCl (Ⅴ)

0.35 g of 4 ¹ -epi-danorubicin hydrochloride (IV) dissolved in a mixture of 5 ml of anhydrous methanol, 14 ml of dioxane and 0.35 ml of ethyl orthoformate was dissolved in 1.4 ml of a 0.93 g bromine solution in 10 ml of chloroform. Process. After 3 hours at 10 ° C. the reaction mixture is poured into a mixture of 70 ml of methyl ether and 35 ml of petroleum ether. The resulting red precipitate is filtered and washed several times with ethyl ether to completely remove the acid and then dissolved in a mixture of 10 ml of acetone and 10 ml of 0.025N aqueous hydrobromic acid. After 15 hours at room temperature 6 ml of water are added to the mixture and the solution is extracted several times with chloroform to remove aglycone. The aqueous phase is then extracted with normal-butanol until the extract is colorless. The mixed organic solvent extract (normal-butanol) was evaporated in vacuo to a small amount (about 6 ml) and precipitated with ethyl ether to yield 0.30 g of 14-bromo derivative. The 14-bromoderivative compound is dissolved in 7 ml of 0.25N hydrobromic acid and treated with 0.5 g sodium formate in 5 ml of water. The reaction mixture is stirred for 48 hours at room temperature, then 1N hydrochloric acid is added to bring the pH to 4. The resulting mixture is extracted with a mixture of ethyl ether and ethyl acetate 1: 1 to remove lipophilic impurities. The aqueous phase is adjusted to pH 7.6 by addition of sodium bicarbonate and then extracted repeatedly with chloroform until colorless. The chloroform extracts are combined, dried over sodium sulfate and evaporated in vacuo to a small amount (about 30 ml). The resulting red solution was adjusted to pH 3.5 with anhydrous methanolic hydrochloric acid and mixed with excess ethyl ether to yield 0.20 g of 4'-epidoxorubicin hydrochloride (V). Melting point 185 ° C. (decomposition): [α] _D ²⁰ + 274 ° (C = 0.01, MeOH): thin layer chromatography on silica gel plate buffered at pH 7 (0.067M phosphate), solvent system CHCl ₃ -MeOH-H ₂ O (Capacity ratio 130: 60: 10), Rf 0.55.

Claims (1)

C-4 by treating N-trifluoroacetyl-danorubicin of formula (I) dissolved in anhydrous methylene chloride with dimethylsulfoxide activated by trifluoroacetic anhydride at a temperature of -65 ° and -60 ° C. 'Oxidize the hydroxyl group, basicize the reaction mixture with 1,5-diazobicyclo (4.3.0) non-5-ene, and then use 4'-keto-N-trifluoro Roacetylacetylunorubicin was obtained and dissolved in methanol, and selectively and stereospecifically reduced with sodium borohydride at a temperature of −10 ° C. to give the corresponding 4′-hydroxy derivative (III), 0.1N After weakly alkaline hydrolysis of the N-trifluoroacetyl group with an aqueous sodium hydroxide solution, the free glycoside base 4'-epi-danorubicin is obtained, and then treated with methanolic hydrochloric acid to give the corresponding hydrochloric acid. Isolated as (IV) and treated with bromine dissolved in a mixture of methanol-dioxane and dissolved in chloroform in the presence of ethyl orthoformate to give the corresponding 14-bromo derivative, and finally at room temperature in aqueous sodium formate solution Hydrolyzing to obtain 4'-epidoxorubicin as hydrochloride (V) thereof to obtain 4'-epidoxorubicin of formula (V).