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 310
helical conformation and can be cyclized, via ring-closing
metathesis, to the corresponding cyclic tetrapeptides without
disrupting the helical conformations in CDCl3 as well as in
DMSO-d6 solutions. The detailed conformational studies
were carried out by using NMR spectroscopy, X-ray crystallography, molecular dynamic simulations, and circular
dichroism spectroscopy.