Pseudolaric acid B: NMR assignments, conformational analysis and cytotoxicity

Abstract

The proton and carbon spectra for the fertility‐regulating agent, pseudolaric acid B (1), have been assigned using a combination of one‐ and two‐dimensional NMR spectroscopic techniques. NOE difference measurements revealed an unexpected conformation of the molecule, which could only be explained by a strained conformation of the six‐membered lactone ring. Molecular forcefield calculations confirmed the presence of a low‐energy conformer having the lactone ring in a half‐planar conformation. The solution conformation is closely related to the solid‐state conformation. Evaluation in a broad range of human cell lines established that 1 is a general cytotoxic agent.