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Nucleation of β-Hairpin Structures with Cis Amide Bonds in E-Vinylogous Proline-Containing Peptides

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journal contribution
posted on 12.07.2003, 00:00 by Tushar K. Chakraborty, Animesh Ghosh, S. Kiran Kumar, Ajit C. Kunwar
Synthesis and conformational studies of peptides containing the E-vinylogous prolines 1 (VPro1) and 2 (VPro2), Boc-Ala-Val-VPro1-Xaa-Leu-OMe (3, Xaa = Gly; 4, Xaa = Phe), Boc-Ala-Val-VPro2-Xaa-Leu-OMe (5, Xaa = Gly; 6, Xaa = Phe), Boc-Leu-Ile-Val-VPro1-Xaa-Leu-OMe (7, Xaa = Gly; 8, Xaa = Phe), and Boc-Leu-Ile-Val-VPro2-Xaa-Leu-OMe (9, Xaa = Gly; 10, Xaa = Phe), were carried out. It has been shown that both VPro1 and VPro2 lead to the formation of 12-membered intramolecularly hydrogen bonded structures very similar to type VI β-turns with a cis Xaa−VPro amide bond in the major conformers in all the peptides 310, resulting in the nucleation of β-hairpin type structures in these molecules in CDCl3.