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13C NMR signal assignment of friedelin and 3α-hydroxyfriedelan-2-one

✍ Scribed by Hugo E. Gottlieb; Parimi A. Ramaiah; David Lavie

Publisher
John Wiley and Sons
Year
1985
Tongue
English
Weight
532 KB
Volume
23
Category
Article
ISSN
0749-1581

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✦ Synopsis

The 13C NMR spectrum of the pentacyclic triterpene friedelin was fully assigned, taking into account signal multiplicities, correlations of the carbon lines with known proton resonances and Eu-induced shifts. T h i s work clarifies the situation prevalent in the literature, in which three separate groups have published contradictory information. In addition, the carbon and proton spectra of the naturally occurring 3c~-hydroxyfriedelan-2-one and its synthetic acetate were analysed. The different preferred conformations of the D/E rings for friedelin (boat-boat) and polpunonic acid (chair-chair) are rationalized.

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