Absolute stereochemistry of the diepoxins

The exciton coupled CD method has been applied to determine the absolute configuration of the diepoxins, spiroketal-linked naphthodiepoxydecalinones of fungal origin. The CD spectra of the bis-dimethylaminobenzoate derivatives of the diepoxins eta, iota and kappa, reveal a positive chiral twist between the two substituted hydroxyl groups and thus infer the S configuration at both of these stereogenic centers. The absolute configuration of the remaining chiral centers is deduced from their relative configurations as established by X-ray diffraction of diepoxin kappa. The twist boat conformation of the epoxycyclohexanone ring and the continued axial orientation of the substituents at C-4 and C-5 after dimethylaminobenzoate derivatization was corroborated by H-1-NMR coupling constants.