Synthesis and reactivity of beta-bromo-beta-substituted dehydroalanines

Abstract

The methyl ester of N-tert-butoxycarbonyl-(Z)-beta-bromo-beta-(1,2,4-triazol-1-yl)dehydroalanine was prepared by treatment of the methyl ester of N-tert-butoxycarbonyl-(E)-beta-(1,2,4-triazol-1-yl)dehydroalanine with N-bromosuccinimide (NBS), followed by Et3N. The reactivities of this compound and of our previously synthesized methyl ester of N-tert-butoxycarbonyl-beta,beta-dibromodehydroalanine towards several nucleophiles were studied, and it was found that these compounds react with oxygen nucleophiles to give the corresponding alpha-alkoxy-beta,beta-disubstituted alanines. Addition to the a-carbon atom also occurred when the beta,beta-dibromodehydroalanine derivative was treated with primary amines, giving alpha-amino-beta,beta-dibromoalanines. Treatment of the beta-bromo-beta-(1,2,4-triazol-1-yl)dehydroalanine derivative with amines gave alpha-(alkylamino)-beta-(alkylimino)alanines in high yields. These iminoalanines afforded alpha-aminoglycines when treated with silica in dichloromethane. (c) Wiley-VCH Verlag GmbH & Co.