New open-chain and cyclic tetrapeptides, consisting of alpha-, beta(2)-, and beta(3)-amino-acid residues, as somatostatin mimics - A survey

Abstract

Cyclo-β-tetrapeptides are known to adopt a conformation with an intramolecular transannular hydrogen bond in solution. Analysis of this structure reveals that incorporation of a β2-amino-acid residue should lead to mimics of 'α-peptidic β-turns' (cf. A, B, C). It is also known that short-chain mixed β/α-peptides with appropriate side chains can be used to mimic interactions between α-peptidic hairpin turns and G protein-coupled receptors. Based on these facts, we have now prepared a number of cyclic and open-chain tetrapeptides, 7-20, consisting of α-, β2-, and β3-amino-acid residues, which bear the side chains of Trp and Lys, and possess backbone configurations such that they should be capa..