Variable-Temperature <sup>1</sup>H-NMR Studies on Two <em>C</em>-Glycosylflavones

Abstract

Two known <em>C</em>-glycosylflavones, swertisin and embinoidin, were isolated from the leaves of <em>Anthurium aripoense</em>, and characterized by room temperature 1D and 2D NMR experiments. At this temperature, the ¹H- and ¹³C-NMR spectra of these <em>C</em>-glycosylflavones revealed doubling of signals, which suggested the presence of two rotamers in solution. Variable-temperature (VT) ¹H-NMR studies supported this hypothesis. The T-ROESY data, in addition to the theoretical (MM2) calculations utilizing the Chem3D Pro software, confirmed the hypothesis that the two rotamers interchange via rotation about the <em>C</em>-glycosidic bond.

Keywords

• variable-temperature &lt;sup&gt;1&lt;/sup&gt;H-NMR
• &lt;em&gt;C&lt;/em&gt;-glycosylflavones
• rotamers
• swertisin
• embinoidin
• &lt;em&gt;Anthurium aripoense&lt;/em&gt;