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

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