Synthesis and conformational studies of novel cyclic peptides constrained into a 310 helical structure by a heterochiral D-Pro-L-Pro dipeptide template

An acyclic tripeptide based on a heterochiral d-pro-l-pro template shows a propensity to exist as a 3 10 helical conformation and can be cyclized, via ring-closing metathesis, to the corresponding cyclic tetrapeptides without disrupting the helical conformations in CDCl 3 as well as in DMSO-d 6 solutions. The detailed conformational studies were carried out by using NMR spectroscopy, X-ray crystallography, molecular dynamic simulations, and circular dichroism spectroscopy.