Stereoselective acylation of a racemic amine with Cα-methyl phenylglycine-based dipeptide 5(4H)-oxazolones

Reactions of a racemic amine with chiral, N-alpha-acetylated, C-alpha-methyl L-phenylglycine-based dipeptide 5(4H)-oxazolones proceed diastereoselectively to give predominantly dipeptide alkylamides comprising D-alpha-phenylethylamine. Diastereoselectivity is remarkably sensitive to solvent polarity and reaction temperature but not significantly to the nature of the C-alpha-tetrasubstituted alpha-amino acid at position 1 of the dipeptide. The beta-turn 3D structures of the aminolysis products were established in CDCl3 solution by FIF-IR absorption and in one case in the crystal state by X-ray diffraction as well. (C) 2005 Wiley-Liss, Inc.