NMR AND CD SPECTRAL STUDIES OF CONFORMATIONAL ISOMERS OF ISOLIGULARONE AND FUKINONE, NATURALLY OCCURRING cis-DECALIN DERIVATIVES

NMR and CD spectroscopic evidence showed that cis-decalin types of sesquiterpenic ketones, isoligularone (2) and fukinone (3), predominantly adopt “steroid-like” conformations in solution in contrast with ligularone (1) which prefers the “non-steroid-like” one. 13C NMR signal assignments and anomalies in the CD of the furanoketones are also reported.