Conformational preferences of α-substituted proline analogues

Alejandra Flores-Ortega, Ana I. Jiménez, Carlos Cativiela, Ruth Nussinov, Carlos Alemán, Jordi Casanovas

Research output: Contribution to journalArticlepeer-review

Abstract

(Chemical Equation Presented) DFT calculations at the B3LYP/6-31+G(d,p) level have been used to investigate how the replacement of the α hydrogen by a more sterically demanding group affects the conformational preferences of proline. Specifically, the N-acetyl-N′-methylamide derivatives of L-proline, L-α-methylproline, and L-α-phenyl-proline have been calculated, with both the cis/trans isomerism of the peptide bonds and the puckering of the pyrrolidine ring being considered. The effects of solvation have been evaluated by using a Self-Consistent Reaction Field model. As expected, tetrasubstitution at the α carbon destabilizes the conformers with one or more peptide bonds arranged in cis. The lowest energy minimum has been found to be identical for the three compounds investigated, but important differences are observed regarding other energetically accessible backbone conformations. The results obtained provide evidence that the distinct steric requirements of the substituent at Cα may play a significant role in modulating the conformational preferences of proline.

Original languageEnglish
Pages (from-to)3418-3427
Number of pages10
JournalJournal of Organic Chemistry
Volume73
Issue number9
DOIs
StatePublished - 2 May 2008

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