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.