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13C NMR spectral assignment of five epimeric 3alpha- versus 3beta-functionalized cholestane pairs
S S Ramos1, L Santos, P Almeida
1INETI, Instituto Nacional de Engenharia, Tecnologia e Inovação, I.P., Estrada do Paço do Lumiar, 1649-038 Lisboa, Portugal.
Abstract:
(13)C NMR chemical shift assignments of five alpha- and beta- epimeric pairs of cholestanes functionalized at C-3 are presented. Empirical increment estimations proved to be a valuable tool for the unequivocal structural elucidation when compared with the chemical shift values of cholestanes derivatized by introduction of N- and S-containing groups at C-3 in equatorial and axial positions. Moreover, the possibility is demonstrated to anticipate the effect of -OC(S)R substituents at neighboring carbon atoms of the ring A backbone.
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