Structure Determination of a New Chromone Glycoside by 2D INADEQUATE NMR and Molecular Modeling

Abstract

The structure of a new chromone glycoside isolated from smilax glabra, named smiglanin [3,5,7-trihydroxychromone 3-O-α-L-rhamnopyranoside] (C15H16O9), was determined using NMR techniques. The carbon skeleton of the molecule was established mainly by the 2D INADEQUATE method coupled with a computerized spectral analysis. Complete 1H and 13C resonance assignments were made based on the INADEQUATE and other 1D and 2D NMR techniques, including long-range HETCOR and indirect detection HMBC. The vicinal proton–proton coupling constants, together with proton–proton distance constraints derived from the NOESY experiment, were incorporated as molecular modeling parameters to give the energetically most favorable conformation.