ABSOLUTE STEREOCHEMISTRY OF THE DIEPOXINS

The exciton coupled CD method has been applied to determine the absolu te configuration of the diepoxins, spiroketal-linked naphthodiepoxydec alinones of fungal origin. The CD spectra of the bis-dimethylaminobenz oate derivatives of the diepoxins eta, iota and kappa, reveal a positi ve chiral twist between the two substituted hydroxyl groups and thus i nfer the S configuration at both of these stereogenic centers. The abs olute configuration of the remaining chiral centers is deduced from th eir relative configurations as established by X-ray diffraction of die poxin kappa. The twist boat conformation of the epoxycyclohexanone rin g 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.