STRUCTURAL-ANALYSIS OF BETA-TURN MIMICS CONTAINING A SUBSTITUTED 6-AMINOCAPROIC ACID LINKER

A series of beta-turn models have been prepared consisting of the dipe ptide Ala-Gly cyclized with all stereoisomers of 6-amino-3,5-dimethylc aproic acid and 6-amino-3-methylcaproic acid, as were related peptides based on Gly-Gly and Ala-Ala, The requisite linkers were made using r outes featuring stereoselective ring-expansion reactions and the synth eses completed using standard methodology. A preliminary examination o f these compounds has been carried out using NMR spectroscopy, circula r dichroism, and, in several cases, X-ray crystallography. These studi es indicate that, depending on linker stereochemistry, different propo rtions of type II and type I turns were observed in solution. Both typ e I and type II turns were observed in the solid state.