Synthesis of Analogues of GABA. II. 4-Alkyl-4-aminobut-2-enoic Acids and a New Synthesis of Some Vinyl α-Amino Acids

Abstract

A series of 4-alkyl-4-aminobut-2-enoic acids (2)-(5) has been prepared as conformationally restricted analogues of GABA. The synthetic route which involved allylic bromination followed by displacement with ammonia also gave vinyl glycine analogues (7)-(9) as readily purified by-products of the reaction. The low biological activity in vitro against GABA uptake, binding and enzyme systems of (E)-2-aminocyclohexylideneacetic acid (4) and (E)-2-aminocyclopentylideneacetic acid (5) has been interpreted in terms of steric hindrance by the ring-forming methylene groups at the particularactive sites concerned.