STRUCTURE DETERMINATION OF A NEW CHROMONE GLYCOSIDE BY 2D INADEQUATE NMR AND MOLECULAR MODELING

The structure of a new chromone glycoside isolated from smilax glabra, named smiglanin [3,5,7-trihydroxychromone 3-O-alpha-L-rhamnopyranosid e] (C15H16O9), was determined using NMR techniques. The carbon skeleto n of the molecule was established mainly by the ZD INADEQUATE method c oupled with a computerized spectral analysis. Complete H-1 and C-13 re sonance 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 pro ton-proton distance constraints derived from the NOESY experiment, wer e incorporated as molecular modeling parameters to give the energetica lly most favorable conformation.