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Stereochemical analysis of the 3α‐ and 3β‐hydroxy metabolites of tibolone through NMR and quantum‐chemical investigations. An experimental test of GIAO calculations
Author(s) -
Colombo Diego,
Ferraboschi Patrizia,
Ronchetti Fiamma,
Toma Lucio
Publication year - 2002
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.1064
Subject(s) - geminal , chemistry , chemical shift , molecule , computational chemistry , tibolone , nuclear magnetic resonance spectroscopy , carbon 13 nmr , proton , proton nmr , stereochemistry , organic chemistry , physics , quantum mechanics , menopause , biology , genetics
Abstract The configuration at C‐3 of the 3α‐ and 3β‐hydroxy metabolites of tibolone was studied by extensive application of one‐ and two‐dimensional 1 H and 13 C NMR spectroscopy combined with molecular modeling performed at the B3LYP/6–31G(d) level. Using HF and DFT GIAO methods, shielding tensors of the two molecules were computed; comparison of the calculated NMR chemical shifts with the experimental values revealed that the density functional methods produced the best results for assigning proton and carbon resonances. Although steroids are relatively large molecules, the present approach appears accurate enough to allow the determination of relative configurations by using calculated 13 C resonances; the chemical shift of pairs of geminal α/β hydrogen atoms can also be established by using calculated 1 H resonances. Copyright © 2002 John Wiley & Sons, Ltd.