S. Maricic, U. Berg, T. Frejd
Apr 8, 2002
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Influential Citations
24
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Journal
Tetrahedron
Abstract
Solution phase synthesis of a constrained Leu(5)-enkephalin amide analogue 10 is reported, in which the cyclic ferrocenyl containing subunit 7 was introduced as a mimetic of the tetrapeptide Tyr-Gly-Gly-Phe unit. Temperature dependence of the chemical shift of the amide protons of 10 indicated a hydrogen bond between the same amino acid residues as observed for the natural Leu-enkepalin in the single-bend conformation. The rotational barrier (DeltaG(c)(not equal)=16.8 kcal/mol) of the C-terminal amide group, which was determined by DNMR spectroscopy, and NOESY experiments indicated that the two termini were more distant as compared to the single-bend conformation of natural Leu-enkephalin amide. (C) 2002 Elsevier Science Ltd. All rights reserved. (Less)