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Absolute Configuration of Kelsoene and Prespatane
K Nabeta1, M Yamamoto, H Koshino
1a Department of Bioresource Science, Obihiro University of Agriculture and Veterinary Medicine.
Abstract:
The absolute configurations of the rare sesquiterpenes, kelsoene and prespatane, were determined to be (1S, 2R,5S, 6S, 7R, 8R)-2,8-dimethyl-6-(1-methylethenyl)tricyclo[5.3.0.0(2,5)] decane (IUPAC name) and (1R, 2S, 5R, 6R, 7R, 8S)-1,5-dimethyl-8-(1-methylethenyl) tricyclo-[5.3.0.0(2,6)] decane, respectively, on the basis of the observed chemical shifts and NOEs in NOESY and NOEDS experiments after conversion with the chiral reagent, 2'-methoxy-1,1'-binaphthalene-2-carbohydroximoyl chloride (MBCC). The absolute configurations of kelsoene and prespatane thus determined suggest that initial cyclization of FPP from the si-face at C-10 to form a 10R-germacradienyl cation leads to kelsoene, while that from the re-face leads to prespatane via the 10S-germacradienyl cation.
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