Conformational heterogeneity of tripeptides containing Boc-Leu-Aib as corner residues in the solid state

Haldar, D., Drew, M.G.B. and Banerjee, A. (2007) Conformational heterogeneity of tripeptides containing Boc-Leu-Aib as corner residues in the solid state. Tetrahedron, 63 (25). pp. 5561-5566. ISSN 0040-4020 doi: 10.1016/j.tet.2007.04.026

Abstract/Summary

A critical analysis of single crystal X-ray diffraction studies on a series of terminally protected tripeptides containing a centrally positioned Aib (alpha-aminoisobutyric acid) residue has been reported. For the tripeptide series containing Boc-Ala-Aib as corner residues, all the reported peptides formed distorted type II beta-turn structures. Moreover, a series of Phe substituted analogues ( tripeptides with Boc-Phe-Aib) have also shown different beta-turn conformations. However, the Leu-modified analogues (tripeptides with Boc-Leu-Aib) disrupt the concept of beta-turn formation and adopt various conformations in the solid state. X-ray crystallography sheds some light on the conformational heterogeneity at atomic resolution. (c) 2007 Elsevier Ltd. All rights reserved.