A new synthesis of α-amino-acids by the reaction of Grignard reagents with ethyl N-trichloroethylidenecarbamate

The reactions of methyl-, ethyl-, n-propyl-, n-butyl-, allyl-, and benzyl-magnesium halides with ethyl N-trichloroethylidenecarbamate (1) gave 1-substituted ethyl 2,2,2-trichloroethylcarbamates, which afforded α-amino-acids on hydrolysis and decarboxylation. By this method DL-alanine and DL-norleucine were obtained in 53 and 60% overall yields, respectively. When branched alkyl Grignard reagents such as isopropyl-, isobutyl- and s-butyl-magnesium bromide were used, attack on the imino-group was hindered by the trichloromethyl group and only reduction occurred to give ethyl 3,3-dichloro-1-ethoxycarbonyl-4-trichloromethylazetidin-2-ylcarbamate (4) and ethyl [2,2,2-trichloro-1-(N-ethoxycarbonyl-2,2,2-trichloroethylamino)ethyl]carbamate (5).