A C15hydrocarbon isolated from the leaves of 2 wild tomato species, Lycopersicon hirsutum f glabratum PI 199381 and Lycopersicon hirsutum PI 365906, has been identified as 7 - epizingiberene (2), a diastereomer of zingiberene (1) that occurs in essential oil of ginger. The structure assignment for 2 is based upon its1H NMR,13C NMR, IR, UV, and mass spectral characteristics. All spectral data for zingiberene and epizingiberene are identical except for 9 of 1513C NMR resonances, which establish the diastereomeric relationship of these sesquiterpenes. The 4S, 7R stereochemistry of epizingiberene was proven by dehydrogenation to (7R)- ar - curcumene (4). The opposite 7R and 7S stereochemistry of the zingiberenes implicates the probable occurrence of opposite sidechain rotations of a common (S)-bisabolyl carbocation intermediate (1OA) to allow stereoelectronically favorable hydride shifts in their respective biosyntheses from (E, E)-farnesyl diphosphate. © 1994.
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