Method of preparing gamma-L-glutamyl taurine

A method of preparing gamma-L-glutamyl taurine which comprises the steps of:

• (a) reacting carbobenzyloxy-L-glutaminic acid-.alpha.-benzyl ester with a substantially equivalent quantity of triethylamine and a substantially equimolar quantity of isobutylchloroformate, then stirring the reaction mixture with cystamine dihydrochloride, and recovering N,N'-bis-(N-carbobenzyloxygamma-L-glutamyl)-cystamine;
• (b) treating the N,N'-bis-(N-carbobenzyloxygamma-L-glutamyl)-cystamine obtained in step (a) with hydrogen peroxide in lacial acetic acid to produce carbobenzyloxy-gamma-(.alpha.-benzyl)-L-glutamyl-taurine;
• (c) dissolving the carbobenzyloxy-gamma-(.alpha.-benzyl)-L-glutamyl-taurine obtained in step (b) in an alkali hydroxide solution, treating an ion-exchange resin with the resulting solution, eluting said treated resin with water and evaporating the eluate to produce carbobenzyl-gamma-L-glutamyl-taurine;
• and
• (d) subjecting the carbobenzyloxy-gamma-L-glutamyl-taurine to acidolysis to produce gamma-L-glutamyl-taurine.