Epoxidation of Peptidyl Olefin Isosteres. Stereochemical Induction Effect of Chiral Centers at Four Adjacent Cα Positions

Four tripeptidyl olefin isosteres were prepared, each of which contains a single chiral center derived from the bulky amino acid phenylalanine at positions corresponding to the P2–P′2 positions of a protease substrate. The effect of these chiral centers on the stereochemical outcome of mCPBA epoxidation of the olefin functionality was studied. A chiral center at P2 or P′2 position has no significant effect, and the P′1 position exerts a small stereoselectivity. A chiral center at the P1 position, on the other hand, has a profound chiral induction effect on the epoxidation reaction.