Molecular dynamics and NMR analysis of the configurational 13C assignment of epimeric 22,23-epoxides of stigmasterol

Reynier Suardíaz, Mitcheell Maestre, Suárez Ernesto, Yamilet Bernardo, Esther Alonso-Becerra, Carlos Pérez*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The determination of the stereochemistry of brasinosteroid analogs with 22,23-epoxide groups can be easily achieved by means of 13C NMR spectroscopy. Here, we provide a rationalization of the 13C chemical shift pattern found in 22R,23R- and 22S,23S-epoxides of stigmasterol, based on the analysis of γ effects. (22S,23S)and (22R,23R)-3β-acetoxystigmast- 22,23-epoxy-5,6β-diol were used in the study as model compounds. Our methodology starts with a conformational search by means of molecular dynamics and NMR (NOE contacts) spectroscopy, which is followed by the analysis of the different γ interactions affecting the chemical shift of interest. We demonstrate that the differences between the 13C chemical shift patterns of 22R,23R and 22S,23S isomers arise from γ effects as the result of diverging local conformations around the C17-C20 and C20-C22 bonds.

Original languageEnglish
Pages (from-to)8333-8336
Number of pages4
JournalJournal of Physical Chemistry A
Volume112
Issue number36
DOIs
Publication statusPublished - 14 Aug 2008

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