SCSA Code: Applications on the Cyclopeptide Renieramide

Abstract

SCSA is an algorithm designed to get information on molecular conformational properties. The most stable conformers are determined by the homemade SCSA code, performing a multistep systematic conformational search, which involves energy and structure quantum chemical optimizations at low-level and high-level. The SCSA method was employed to analyze the conformational space of the in vacuo cyclopeptide renieramide at AMI and B3LYP/6-31G(d) levels. Calculations at B3LYP level of the GIAO 13C NMR chemical shifts were also performed on the final conformers. In fact, to validate the conformational search results experimental and calculated 13C NMR spectra of renieramide were compared. Slight disagreements observed between experimental and calculated spectra could be attributed to solute-solvent interactions, which were not taken into account in the algorithm proposed here.