Please use this identifier to cite or link to this item: http://repositorio.unicamp.br/jspui/handle/REPOSIP/58505
Type: Artigo de periódico
Title: Pyrrolizidine alkaloids necine bases: II. Conformational analysis of free bases
Author: Giordan, M
Abstract: Molecular mechanics calculations were applied to the conformational analysis of two diasteroisomers, the pyrrolizidine alkaloids (PAs) retronecine and heliotridine. The application of reoptimized parameters for H bonding corrected the tendency of MM3(92) calculations to give unrealistic H ... O distances for intramolecular OH interactions occurring in both diasterisomers. Inversions in the H-bond direction of exo-retronecine and in the relative stability of heliotridine endo-exo conformers were also observed with the application of the new parameters. A set of probable conformers was obtained for each diasterisomer, based on conformational and Boltzmann population analysis. Only exo-puckered conformers were found in the retronecine set, whereas both exo- and endo-puckered conformers were obtained for heliotridine. Transition state conformations supplied arguments supporting the design of models for H-bond interconversion in the case of exo-retronecine and for the exo-endo interconversion of heliotridine. Reactivity behaviors and H-1-NMR data of both diasterisomers were elucidated in light of the theoretical results. (C) 1998 John Wiley & Sons, Inc.
Subject: pyrrolizidine alkaloids
necine bases
retronecine
heliotridine
conformational analysis
molecular structure
hydrogen bond
molecular mechanics
Country: EUA
Editor: John Wiley & Sons Inc
Rights: fechado
Date Issue: 1998
Appears in Collections:Unicamp - Artigos e Outros Documentos

Files in This Item:
File Description SizeFormat 
WOS000077130900006.pdf334.76 kBAdobe PDFView/Open


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.