STEREOCHEMISTRY OF NEOLIGNANS - A REVISED STRUCTURE FOR A NEOLIGNAN ISOLATED FROM THE ROOTS OF PIPER-CAPENSE

The erythro 8-O-4' neolignan IIIb was synthesized and was found to have identical H-1 and C-13 NMR characteristics to a neolignan reported as a component of the roots of Nardostachys jatamansi. The NMR spectral characteristics of compound IIIb were also identical with those of a neolignan previously obtained from the roots of Piper capense, for which the unlikely 8-O-3' structure IVa had been proposed. Two further erythro 8-O-4' compounds IIIc and IIId were prepared, and their assigned C-13 NMR signals were consistent with those of IIIb. At this time, there appears to be no evidence for the existence of 8-O-3' neolignans as plant extracts.