Process for preparation of optically active N-mercaptoalkanoylamino acids

Claim 1

A process for the preparation of an optically active N-mercaptoalkanoylamino acid represented by formula (I): ##STR16## wherein R 1 is lower alkyl having from 1 to 4 carbon atoms, Y is (CH 2 ) n , n being 1 or 2, or sulfur, and Q is hydroxy or the residual part of an amino acid represented by formula (II): ##STR17## wherein R 2 is lower alkyl having from 1 to 4 carbon atoms or benzyl, which comprises (1) reacting an optically active β-hydroxyalkanoic acid represented by formula (III): ##STR18## wherein R 1 is the same as defined above, with thionyl chloride or thionyl bromide in the presence of a catalyst by keeping the temperature of the reaction mixture at not more than 25° C. when said thionyl chloride or thionyl bromide is mixed with the compound (III) and then raising the temperature of the reaction mixture up to from about 30° C. to about 100° C. to prepare an optically active β-haloalkanoyl halide represented by formula (IV): ##STR19## wherein X is chlorine or bromine and R 1 is the same as defined above; (2) reacting the β-haloalkanoyl halide with an amino acid represented by formula (V): ##STR20## wherein Y and Q are the same as defined above, to produce an optically active N-β-haloalkanoylamino acid represented by formula (VI): ##STR21## wherein X, R 1 , Y and Q are the same as defined above; and (3) reacting the N-β-haloalkanoylamino acid with an alkali metal salt of hydrogen sulfide or ammonium hydrosulfide, of which the molar ratio to the compound (VI) is from about 2 to about 10, in water or a polar aprotic solvent at a temperature of from about 60° C. to about 90° C., the configuration of the formulas (II), (III), (IV), (V), and (VI) being retained in all the optically active compounds throughout the process to prepare the compound represented by formula (I).