Solution conformational preferences of a peptidic analogue of a natural macrolide

The conformational behavior in solution of a cyclic peptide with sequence cyclo(Pro'-Pro2-Dab3(cHexA)ili[N-'HCO}-Leu4<fj[NHCO}-Suc5-Gly6-) has been throughly investigated with the combined use ofnmr and molecular dynamic techniques. The compound, which has been modeled to mimic the FK506 macrolide bound to the FK506 binding protein structure, can be considered as a peptidic analogue of the FK506 system. Tlie synthesis was carried out on a phenylacetoamidomethyl resin using an appropriate protocol for the peptide chain elongation. The conformational properties of the cyclic hexapeptide were studied in DMSO and water. The nmr data in DMSO and restrained molecular dynamics simulations show the presence of Mo contiguous cis peptide bonds involving the -Gly-Pro-Prosegment. This segment in water exhibits conformational heterogeneity presenting at least ftvo distinct conformational families, characterized the first by a cis-cis and the second by a transcis Gly-Pro-Pro configuration; the trans-cis isomer was fully characterized. ©1997 John Wiley & Sons, Inc.