Reaction of S-(2-amino-2-carboxyethylsulfonyl)-l-cysteine with sulfite: Synthesis of S-sulfo-l-cysteine and l-alanine 3-sulfinic acid and application to the determination of sulfite☆☆☆★

Abstract A procedure for the simultaneous preparation of S -sulfo- l -cysteine and l -alanine 3-sulfinic acid is described. The method is based on the quantitative reaction between sulfite and S -(2-amino-2-carboxyethylsulfonyl)- l -cysteine. The yield was 95% for S -sulfo- l -cysteine and 91% for l -alanine 3-sulfinic acid. The reaction was also applied to the quantitative determination of sulfite in biological materials. In this procedure, sulfite reacts with S -(2-amino-2-carboxyethylsulfonyl)- l -cysteine. Separation of the reaction product, S -sulfo- l -cysteine, is done by ion-exchange fractionation, and it is determined with acid ninhydrin reagent 2 ( M. K. Gaitonde, 1967, Biochem. J. 104, 627–663 ). The recovery was 96.8 ± 0.3%.