To obtain the subject compound useful e.g. as an intermediate for pharmaceuticals and agrochemicals in high purity by adjusting an enzymatic reaction liquid containing S-phenyl-L-cysteine to a strongly acidic state to effect the dissolution of the crystal, treating with activated carbon under aeration, separating the insoluble component. neutralizing the filtrate and collecting the produced crystal.
The objective S-phenyl-L-cysteine is produced in high purity by carrying out the enzymatic reaction of thiophenol with a βsubstituted-L- alanine expressed by formula [X is OR (R is H, an alkyl, an aryl, etc.) or SR] using tryptophan synthase, etc., as a catalyst to form S-phenyl-L-cysteine, adjusting the pH of the liquid to a strongly acidic state of ≤1.5 after completing the enzymatic reaction to effect the dissolution of the S-phenyl-Lcysteine crystal precipitated in the reaction liquid, adding activated carbon to the solution, keeping the solution at 20-60°C while passing air or oxygen through the solution, separating and removing the activated carbon and insoluble components from the solution by filtration, adjusting the pH of the filtrate to 2.5-6.0 by the addition of an alkali and separating the precipitated crystal.
KOITO MITSUO
OSABE MASAMI
SAKAGUCHI AKIO
FUKUHARA NOBUHIRO
