Synthesis of cyclic β-turn mimics from l-Pro-Phe/Phe-l-Pro derived di- and tripeptides via ring closing metathesis: the role of chirality of the Phe residue during cyclization

Pent-4-enoyl-l-Pro-Phe-N-allyl/pent-4-enoyl-Phe-l-Pro-N-allyl and pent-4-enoyl-l-Phe-Pro-Gly-N-allyl/pent-4-enoyl-Gly-Pro-Phe-N-allyl amide derived di- and tripeptides can be cyclized leading to β-turn mimics via ring closing metathesis using Grubbs’ catalyst. The chirality of the Phe residue in these di- and tripeptides controls the cyclization during ring closing metathesis. The presence of pent-4-enoyl and allyl groups at the termini of these peptides leads to the concomitant formation of the amino acid, 4,5-dehydro-6-aminocaproic acid, as a linker, during cyclization.