Patent GB-811103-A (GB)
Title: Amino acid compounds and methods for producing the same
IPC: C07C245/18
Filed: 1956-04-24
Abstract: The invention comprises 6-diazo-5-oxonorleucine (DON) including its optical enantiomorphs, alkali and alkaline earth metal salts, the C1-4 alkyl and benzyl esters thereof and the N-trifluoroacetyl derivatives of all these compounds; and their preparation by the following methods: (1) hydrazine is reacted with an alkyl ester or an alkali or alkaline earth metal salt of 6-diazo-5-oxo-N-phthaloylnorleucine to give the corresponding ester or salt of DON, which may then be hydrolysed with aqueous alkali below room temperature and/or neutralized, preferably at pH 5.5 to 7. Two to three equivalents of hydrazine are preferably used at below about 50 DEG  C.  (2) 6-Amino-5-oxonorleucine, preferably used in acid-addition salt form, is diazotized, suitable diazotizing agents being nitrous acid, as a solution or generated in situ, alkyl nitrites and nitrosyl compounds.  (3) Glutamic acid a -benzyl ester is reacted with at least one equivalent of a halogenating agent, preferably at below 50 DEG  C., and the resulting 4-carbobenzoxy-4-aminobutyryl halide is reacted in the cold with at least three equivalents of diazomethane to give 6-diazo-5-oxonorleucine benzyl ester which may then be hydrolysed with aqueous alkali at below 30 DEG  C. and neutralized at pH 5.5 to 7.  The reaction with diazomethane is advantageously performed at from -5 DEG  to 10 DEG  C. in an inert anhydrous organic solvent. (4) Gamma-benzyl-N-carboxyglutamate anhydride is hydrogenolysed, preferably in presence of a noble metal at a hydrogen pressure of 10 to 60 p.s.i., the resulting N-carboxyglutamate anhydride is reacted with at least one equivalent of a halogenating agent to give a 4-halocarbonylethyloxazolidine-2:5-dione, this is reacted in the cold with at least two equivalents of diazomethane and the resulting 4-(4-diazo-3-oxobutyl)-oxazolidine-2:5-dione is hydrolysed in an aqueous medium below 30 DEG  C. and neutralized at pH 5.5 to 7 to give DON.  The reaction with diazomethane is advantageously performed at -5 to 10 DEG  C. in an inert organic solvent and the hydrolysis is preferably carried out in an alkaline medium.  (5) N-trifluoroacetylglutamic acid is reacted with at least one equivalent of acetic anhydride, preferably at below 100 DEG  C., the resulting N-trifluoroacetylglutamic anhydride is reacted with an alcoholic agent R11OM (R11 being C1-4 alkyl or benzyl and M hydrogen or an alkali metal) to give a mixture of the a -R11-ester and gamma-R11-ester of N-trifluoroacetylglutamic acid, the a -ester, free from or admixed with the gamma-ester, is reacted with at least one equivalent of a halogenating agent to give 4-carbobenzoxy- or 4-carbalkoxy-4-trifluoroacetamido-butyryl halide and this is reacted in the cold, preferably at -5 DEG  to 10 DEG  C., with at least two equivalents of diazomethane to give 6-diazo-5-oxo-N-trifluoroacetylnorleucine which may then be hydrolysed with aqueous alkali at below 30 DEG  C. and neutralized at pH 5.5 to 7 and preferably 6 to 6.5 below room temperature to DON. Advantageously the alcoholic agent is sodium methoxide and the reaction therewith is carried out at below room temperature; and a preferred halogenating agent is thionyl chloride used at 50 DEG  to 80 DEG  C.  (6) A sterile aqueous nutrient medium of pH between 5.0 and 8.5 and containing sources of carbon and nitrogen and inorganic salts is inoculated with Streptomyces C-2943, the resulting mixture is incubated under sterile, preferably submerged, aerobic conditions at between about 20 DEG  and 35 DEG  C., and preferably between 23 DEG  and 29 DEG  C., for a sufficient length of time for the production of L-DON, the solid material is removed and this product is isolated from the aqueous culture liquid. Advantageously, the nutrient medium contains at least one of the following in total quantity between 1.5 and 2 per cent of the total weight of the medium: soybean oil meal, wheat gluten meal, brewers' yeast, saline extracted hog stomach, meat protein hydrolysate, distillers' solubles, corn steep solids, soybean peptone and acid hydrolysed casein.  The medium also preferably contains up to 2 per cent glucose or galactose and 0.1 to 0.5 per cent of an inorganic ammonium salt. The L-DON may be isolated by concentrating the culture liquid, e.g. to one fifth to one twentieth of its original volume, adding 3 to 10 volumes of a water-miscible organic solvent, separating precipitated impurities, contacting the solution with an adsorbent such as alumina of pH 5 to 8, eluting the product from the adsorbent with an eluant such as water or an aqueous solution of an organic solvent, e.g. ethanol, and recovering the product from the eluant. For further purification the L-DON so obtained may be formed into a dilute aqueous solution containing a minor proportion of a water-miscible organic solvent, the pH adjusted to 6 to 7, the solution contacted with active carbon, the adsorbed L-DON eluted with water containing less than 25 per cent of a water-miscible organic solvent, preferably acetone, and the eluant removed.  In examples: (1) L-6-diazo-5-oxo-N-phthaloylnorleucine methyl ester with hydrazine hydrate in methylene chloride gives L-6-diazo-5-oxonorleucine methyl ester which is hydrolysed with methanolic NaOH at 0 DEG  C. to give, on acidification and evaporation of the solvent, a product which is freeze dried, dissolved in water containing acetone, adsorbed in a column of activated carbon and diatomaceous earth, eluted with aqueous acetone and freeze dried to give L-DON; it is stated that the D-isomer is prepared similarly; (2) DL-DON is prepared similarly; (3) L-DON is prepared from L - 6 - diazo - 5 - oxo - N - phthaloylnorleucine potassium salt (prepared by hydrolysis of the methyl ester with methanolic potassium carbonate) and hydrazine hydrate in methanol and purified by a similar method to (1); it is stated that the D-isomer is prepared similarly; (4) DL-6-amino-5-oxonorleucine dihydrochloride is diazotized with sodium nitrite to give DL-DON which is purified by a similar method to (1); it is stated that L-DON and D-DON can be prepared similarly; (5) L-glutamic acid a -benzyl ester with Cbl5 in acetyl chloride gives L-4-carbobenzoxy-4-aminobutyryl chloride hydrochloride, this with diazomethane in ether gives L-6-diazo-5-oxonorleucine benzyl ester and this on hydrolysis and purification as in (1) gives L-DON; it is stated that DL- and D-DON are prepared similarly; (6) L-4-(4-diazo-3-oxobutyl) oxazolidine - 2:5 - dione is hydrolysed with aqueous NaOH, the solution acidified and the product isolated and purified as in (1) to give L-DON; it is stated that D- and DL-DON are prepared similarly; (7) N-trifluoroacetyl-L-glutamic acid and acetic anhydride give N-trifluoroacetyl - L - glutamic anhydride and this on treatment with sodium methoxide in methanol gives a mixture of the alpha- and gammamethyl esters of N-trifluoroacetyl-L-glutamic acid, the former predominating (and it is stated that the benzyl esters can be prepared similarly using sodium benzylate in benzyl alcohol); also the a -benzyl ester is prepared free of the gammaester by reacting L-glutamic acid a -benzyl ester and ethyl thioltrifluoroacetate in dilute alkali at 23-24 DEG  C., and the a -methyl ester is prepared free of the gamma-ester by reacting L-glutamic acid gamma-benzyl ester and ethyl thioltrifluoroacetate in dilute alkali to give N-trifluoroacetyl-L-glutamic acid gamma benzyl ester, esterifying this with diazomethane to give N-trifluoroacetyl-L-glutamic acid alpha-methylgamma-benzyl ester and hydrogenolysing this over palladium-charcoal; the mixture of N-trifluoroacetyl-L-glutamic acid a - and g -methyl ester with thionyl chloride gives a mixture of L - 4 - carbomethoxy - 4 - trifluoroacetamidobutyryl chloride and L-2-trifluoroacetamido-4-carbomethoxybutyryl chloride, this mixture with diazomethane in ether in the cold gives a product containing methyl L-6-diazo-5-oxo-N-trifluoroacetylnorleucine ester and this product on treatment with methanol and sodium hydroxide in the cold with subsequent acidification gives a product containing L-DON, which is purified by a similar method to (1); (8) a nutrient medium containing maltose, butanol-acetone fermentation residue, acid hydrolysed casein, calcium carbonate, sodium chloride and water is adjustde to pH 7.5 with sodium hydroxide, sterilized and inoculated with a castile soap solution suspension of Streptomyces C-2943 to give on incubation and filtration a solution containing L-DON, isolated as described in (9); (9) a nutrient medium containing glucose monohydrate, soybean oil meal, hog stomach saline extracted, ammonium chloride, sodium chloride, calcium carbonate, water and sufficient sodium hydroxide to give a pH of 7.5 is sterilized and inoculated with a sodium heptadecyl sulphate solution suspension of Streptomyces C-2943, the incubated medium is filtered, the filtrate is concentrated, ethanol is added, the solution is filtered, the filtrate is adsorbed on a column o activated alumina, the column is eluted with aqueous ethanol and the eluate freeze dried, the dried material is dissolved in aqueous acetone and the solution adsorbed on a column of activated carbon and diatomaceous earth, and the column is eluted with aqueous acetone and chosen fractions are freeze dried to give pure L-DON; and (10) a procedure similar to (9) also gives pure L-DON.  Specifications 811,104 and 811,105 are referred to.