Structure elucidation of sesbanimide using high-field n.m.r. spectroscopy
Abstract
The structure elucidation of sesbanimide, a novel cytotoxic compound isolated from Sesbania punicea seeds, is based on a detailed study of its high-field 1H and 13C n.m.r. spectra. The conformation and relative configuration of sesbanimide were deduced from the observed proton–proton nuclear Overhauser effects (n.O.e.s) and the magnitude of the proton–proton coupling constants. In solution a solvent-dependent equilibrium exists between the tautomeric ring-closed hemiacetal (1) and the ring-opened γ-hydroxyketone (5) forms of sesbanimide.