SYNTHESES OF OPTICALLY-ACTIVE, PROTECTED AND UNPROTECTED VINYLGLYCINES

Vinylglycine (2) has been shown to undergo racemization under acidic c onditions. Optically pure 2 was obtained from 2.HCl by enzymatic hydro lysis through N'-acetylvinylglycine (5), followed by recrystallization . (S)-N'-(Methoxycarbonyl)vinylglycine (6) was configurationally so un stable under acidic conditions that 6 could not be obtained from 2 in an optically pure form. On the other hand, configurationally stable (S )-N-(9-phenylfluoren-9-yl)vinylglycine methyl ester (9) was synthesize d from (S)-homoserine; 9 was hydrolyzed with sodium hydroxide to affor d the carbocxylic acid 10 of more than 99% ee.