Vinylglycine (2) has been shown to undergo racemization under acidic conditions. Optically pure 2 was obtained from 2·HCl by enzymatic hydrolysis through N-acetylvinylglycine (5), followed by recrystallization. (S)-N-(Methoxycarbonyl)vinylglycine (6) was configurationally so unstable 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 synthesized from (S)-homoserine; 9 was hydrolyzed with sodium hydroxide to afford the carboxylic acid 10 of more than 99% ee.
Benzenesulfonylcarbonitrile oxide. 5. Face selectivity of cycloaddition to chiral terminal alkenes
作者:Peter A. Wade、Shankar M. Singh、M.Krishna Pillay
DOI:10.1016/0040-4020(84)85065-6
日期:1984.1
The diastereomer ratio for cycloaddition of benzenesulfonylcarbonitrile oxide (BSNO) to a series of (S)-vinylglycine-derived alkenes varied from 30:70 to 66:34 depending on the substitutents at the chiral center. Isomer ratios were routinely determined by 1H-NMR; isolation confirmed the results in several cases. Isomer assignment was based on comparison to acivicin where the absolute configuration