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DFT 1 H– 1 H coupling constants in the conformational analysis and stereoisomeric differentiation of 6‐heptenyl‐2 H ‐pyran‐2‐ones: configurational reassignment of synargentolide A
Author(s) -
JuárezGonzález Francisco,
SuárezOrtiz Gloria Alejandra,
FragosoSerrano Mabel,
CerdaGarcíaRojas Carlos M.,
PeredaMiranda Rogelio
Publication year - 2015
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.4178
Subject(s) - chemistry , coupling constant , computational chemistry , pyran , stereochemistry , crystallography , particle physics , physics
Density functional theory (DFT) 1 H– 1 H NMR coupling constant calculations, including solvation parameters with the polarizable continuum model B3LYP/DGDZVP basis set together with the experimental values measured by spectral simulation, were used to predict the configuration of hydroxylated 6‐heptenyl‐5,6‐dihydro‐2 H ‐pyran‐2‐ones 1 , 2 , 4 , and 7 , allowing epimer differentiation. Modeling of these flexible compounds requires the inclusion of solvation models that account for stabilizing interactions derived from intramolecular and intermolecular hydrogen bonds, in contrast with peracetylated derivatives ( 3 , 5 , and 6 ) in which the solvation consideration can be omitted. Using this DFT NMR integrated approach as well as spectral simulation, the configurational reassignment of synargentolide A ( 8 ) was accomplished by calculations in the gas phase among four possible diastereoisomers ( 8–11 ). Calculated 3 J H,H values established its configuration as 6 R ‐[4′ S ,5′ S ,6′ S ‐(triacetyloxy)‐2 E ‐heptenyl]‐5,6‐dihydro‐2 H ‐pyran‐2‐one ( 8 ), in contrast with the incorrect 6 R ,4′ R ,5′ R ,6′ R ‐diastereoisomer previously proposed by synthesis ( 12 ). Application of this approach increases the probability for successful enantiospecific total syntheses of flexible compounds with multiple chiral centers. Copyright © 2014 John Wiley & Sons, Ltd.