New synthetic method of optically active α-methylproline and α-methyl-pipecolinic acid using electrochemical oxidation as a key reaction

A new method for the stereoselective α-methylation of N -protected l -proline and l -pipecolinic acid esters is presented. The method consisted of electrochemical α′-methoxylation of the α-amino acid derivatives, the replacement of the α′-methoxy group with a phenylthio group, α-methylation, and reductive removal of the α′-phenylthio group, successively. The intermediates in this method could be used for the preparation of optically active acyclic α-methylated α-amino acids.