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oai:docta.ucm.es:20.500.14352/927962024-08-01T23:46:30Zcom_20.500.14352_14col_20.500.14352_15

Molecular dynamics and NMR analysis of the configurational C assignment of epimeric 22,23-epoxides of stigmasterol Suardíaz Delrío, Reynier Maestre, Mitcheell Suárez, Ernesto Bernardo, Yamilet Alonso-Becerra, Esther Pérez, Carlos 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. 2024-01-12T12:51:42Z 2024-01-12T12:51:42Z 2024-01-12T12:51:42Z 2008 journal article https://hdl.handle.net/20.500.14352/92796 1089-5639 10.1021/jp804570g 1520-5215 eng Molecular Dynamics and NMR Analysis of the Configurational 13C Assignment of Epimeric 22,23-Epoxides of Stigmasterol Reynier Suardíaz, Mitcheell Maestre, Ernesto Suárez, Yamilet Bernardo, Esther Alonso-Becerra, and Carlos Pérez The Journal of Physical Chemistry A 2008 112 (36), 8333-8336 DOI: 10.1021/jp804570g http://creativecommons.org/licenses/by-nc-nd/4.0/ restricted access Attribution-NonCommercial-NoDerivatives 4.0 International American Chemical Society