Development and Conformational Analysis of a Pseudoproline-Containing Turn Mimic
摘要:
The liquid-phase synthesis and the conformational analysis of a small library of fully protected tetramers containing L-pyroglutamic acid (L-pGlu), (4S,5R)-4-methyl-5-carboxybenzyloxazolidin-2-one (L-Oxd), or (4R,5S)-4-methyl-5-carboxybenzyloxazolidin-2-one (D-Oxd) as residue i + 1 are reported to test the tendency of these oligomers to assume beta-hairpin conformation. The most promising molecule is BOC-L-Val-D-Oxd-Gly-L-Ala-OBn, which assumes a preferential beta-turn conformation in CDCl3, as shown by IR and H-1 NMR analysis. These findings have been confirmed by DFT calculations, which provide an interpretation for the available experimental data and agree with the reported observations.
Pyroglutamic acid as a pseudoproline moiety: a facile method for its introduction into polypeptide chains
作者:Claudia Tomasini、Marzia Villa
DOI:10.1016/s0040-4039(01)00981-9
日期:2001.7
The acylation of benzyl (S)-pyroglutamate is reported by reaction with the pentafluorophenyl ester of protected alanine and threonine. The H-1 NMR analysis of the acylated products shows that the alpha hydrogens of the protected amino acids are very deshielded. This effect is due to the presence of the carbonyl of the lactam ring and shows that the peptide bond is in the trans conformation. The deprotection of the amino acids is also reported. (C) 2001 Elsevier Science Ltd. All rights reserved.