Studies on Optically Active Amino Acids. III. Preparation of 3-(3, 4-Dihydroxyphenyl)-DL-, -D-, and -L-alanine

Abstract

Hydrolyses of the racemate and the optical isomers of 3, 4-methylenedioxyphenylalanine (I), and of their N-acetyl derivatives (DL-, D-, and L-(II)) including the l-menthyl esters (IIIa and IIIb) were smoothly effected by using a mixture of HI, Ac₂O and red phosphorus to furnish the corresponding racemate and optical isomers of 3-(3, 4-dihydroxyphenyl) alanine (Dopa) in fair yields.
This method would be a new and advantageous way for the preparation of DL-, D-, and L-Dopa, when combined with the previously reported preparation of the racemic and optically active intermediates. The absolute configurations of the optical isomers of (I), of their N-acetyl derivatives (D- and L-(I)), and of the l-menthyl esters (IIIa and IIIb) were simultaneously established by the above hydrolyses.