Dedicated to Professor P. T Narasimhan on the occasion of his 75 th anniversary (Abstract Acyclic peptides having pent-4-enoyl at N-terminal and O-allyl at C-terminal as linkers can be transformed to β-turn mimics via ring closing metathesis using Grubb's catalyst. The chirality of Phenylalanine residue controls the cyclization during RCM, which leads to the concomitant formation of 6-hydroxy-caproic acid as a linker during cyclization. amino acids to proline during RCM. The choice of these

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... eptides is dictated by the fact that HIV protease is very specific in cleaving the peptide bond between later two residues and the synthesis of the cyclic β-turn mimics derived especially from Phe-Pro may lead to the development of small inhibitors characterized by high affinity, bioavailability and resistance to proteolytic degradation. In this paper, we report the synthesis of cyclic peptides by ring closing metathesis (RCM) reaction.