Synthesis of βγ-unsaturated α-amino-acids

Abstract

Saponification of methyl N-formylcycloalkylideneglycinates (3) gave N-formylcycloalk-1 -enylglycines (4) through migration of the double bond. The compounds (4) were converted into cycloalk-1-enylglycines (6) by acid hydrolysis. On the results of mechanistic studies it is supposed that the migration is initiated by intramolecular proton abstraction by the carboxylate ion at the γ-position. The method was extended to the synthesis of cycloalk-1-enylglycines containing heteroatoms in the ring [compounds (15)] and isodehydrovaline (17) in high yields.