ABSOLUTE-CONFIGURATIONS OF GONIODIOL, GONIODIOL MONOACETATE AND OTHERRELATED DIHYDROPYRONES FROM SYNTHETIC, CIRCULAR-DICHROISM AND X-RAY CRYSTALLOGRAPHIC EVIDENCE

The absolute configuration of dihydro-7,8-dihydroxystyryl)-5,6-dihydro -2-pyrone] (3) has been unambiguously and independently determined and revised as 7(R),8(R) from the circular dichroism (CD) studies of the diol and its dibenzoate. The 6(R) configuration that follows from its already reported 6,7-threo configuration is also confirmed by the CD s pectrum of 3. Thus, the other congener chemically correlated natural d ihydropyrans (+)-goniodiol monoacetate (2), (+)-goniodiol diacetate (1 ) and (+)-goniotriol (4), isolated from Goniothalamus sesquipedalis (A nnonaceae) must possess the same 6(R),7(R),8(R) absolute configuration . The 6(R) configuration of (+)-goniotriol (4) is predicted from the 5 ,6-threo configuration, based on the J(5,6)-value is well as from biog enetic ground. Synthetic evidences known in the literature for the abs olute configuration of goniodiol and some structurally related natural products have also been incorporated. The X-ray crystallographic stru cture determination of (+)-goniodiol monoacetate (2) unambiguously con firms its 6,7-threo and 7,8-erythro relationship with 6(R),7(R),8(R) c onfiguration. The molecular conformations in solution and crystalline state have also been studied.