Cyclic peptide template combinatorial libraries: synthesis and identification of chymotrypsin inhibitors

A cyclic peptide template combinatorial library in a positional scanning format, composed of three positional libraries, was synthesized using solid-phase chemistry and four orthogonal protecting groups (Fmoc, Boc, Dde, OAll). The cyclic peptide template is composed of three lysine residues and one glutamic acid residue. The chemical diversity was introduced by acylating the epsilon-amino groups of the lysine residues using 10 carboxylic acids in addition to the 20 proteinogenic amino acids. The library components have been shown to be stable towards proteolytic degradation. Compounds with chymotrypsin inhibitory activity were identified through the screening of this library.