Stereoselective synthesis of conformationally restricted analogues of aspartic and glutamic acids from endocyclic enecarbamates.

The stereoselective synthesis of cyclic amino acids incorporating the core framework of aspartic acid and glutamic acids were accomplished from a common intermediate. Oxidative cleavage of an aza-bicyclic-dichlorocyclobutanone/pentanone with Me(2)CuLi/Ac2O followed by ozonolysis furnished the amino acid derivatives in good overall yields in a three-step sequence. This protocol was also applied to the synthesis of a cis-beta-amino acid and to the enantioselective construction of a chimeric amino acid incorporating the basic skeleton of four different naturally occurring amino acids into a single structure. (C) 1997 Elsevier Science Ltd.