Epoxidation of peptidyl olefin isosteres. Stereochemical induction effect of chiral centers at four adjacent C(α) 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. (C) 2000 Elsevier Science Ltd.