Method of preparing D-amino acid-N-(S)- alpha -alkylbenzylamide

摘要

L-amino acid amides are converted to the corresponding D-amino acid amides. An amide formed from an L-amino acid and an optically active (S)- alpha -alkylbenzylamine is subjected to dehydration condensation with an aryl aldehyde to form a Schiff's base, which is racemized at the amino acid moiety in the presence of a base to yield an N-allylidene-D-amino acid-(S)-amide. The less-soluble diastereomer N-allylidene-D-amino acid-(S)-amide is crystallized from the reaction mixture and recovered by means of solid/liquid separation. The N-allylidene form is readily hydrolyzed into the amino acid-(S)-amide and the starting aldehyde.