Stereoselective synthesis and conformational analysis of unnatural tetrapeptides. Part 2

Stereoselective synthesis of unnatural tetrapeptides 20a and 20b, 21a and 21b and 30 and 31, containing two L-valine units and two unnatural alpha-amino acids (ornithine and modified aspartic acid), has been accomplished starting from the L-valine derived chiral synthon 1. Structural investigations of these non-protemogenic peptides have been carried out on the acetamido derivatives using H-1 NMR, IR spectroscopic techniques and a conformational analysis based on molecular dynamics (MD) and cluster analysis. (c) 2007 Elsevier Ltd. All rights reserved.