Abstract
Pharbitic acids C (II) and D (III), the two major constituents of “pharbitic acid” (I), were shown to have the monosaccharide sequences Ha and Ina among the three IIa-c and IIIa-c, respectively, by characterization of their acetolysis products and examination of mass spectra of their perruethylates (XI and XII).
The modes of linkages and conformations of the component monosaccharides were determined by molecular rotation differences and NMR spectra of II, III, and degradation products (IV, V, XIII, XIV and XV) and their permethylates (VI, VII, VIII, IX, XVI, XVII, XI and XII) to be a-conjugation and 1C conformation for L-rhamnoseand β and C1 for D-glucose and D-quinovose.
Consequently II and III are assigned the structures IIa' and IIIa', respectively.
