Conversion of homocystine hydantoin4 to 5-(p-chlorosulfony1)-ethylhydantoin was effected by chlorinating a suspension of the disulfide in water. Treatment of the sulfonyl chloride, suspended in ether, with ammonia or appropriate amine gave the desired sulfonamido- hydantoin. Subsequent hydrolysis of the hydantoin with aqueous barium hydroxide at approximately 160'afforded the corresponding amino acid (Table I). The synthesis of 3-(p- ...