Synthesis of optically Active α-Alkyl or α-Aryl Acids from L-α-Amino Acids by the Use of Organocopper Reagents

Abstract

With an aim to further explore the utility of L-α-amino acids (I) in the synthesis of optically active compounds, the reaction of optically active α-tosyloxy acids and their derivatives (III) readily obtainable from I, with several types of organocopper reagents were studied. Although there still remain some ambiguity in the formation of unusual reaction products such as the β-keto ester (dl-6) and the vicinal diol ((R)(+)-13) and in lower yields for the substitution products, it has become evident that when optically active α-tosyloxy acids prepared from L-phenylalanine, L-alanine, and L-leucine, respectively, are treated with lithium dialkyl- or diarylcuprates, the substitution reactions can proceed with almost full inversion to give corresponding optically active α-alkyl or α-aryl acids in max. 63% yield.