Determination of structure and stereochemistry of tomentosic acid by X-ray crystallography. A novel mechanism for transformation of arjungenin to tomentosic acid
- 1 January 1990
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 8,p. 1445-1450
- https://doi.org/10.1039/p29900001445
Abstract
The molecular geometry of tomentosic acid (1), a tetrahydroxy triterpene acid obtained by acid hydrolysis of arjunglucoside-I, isolated from Terminalia bellerica, has been determined by single-crystal X-ray analysis. The triterpene, C30H48O6, is orthorhombic with space group P212121 and lattice constants a= 15.994(2), b= 14.682(3), c= 11.494(2)Å, cell volume V= 2 699.0 Å3, and Z= 4. Diffractometer intensity measurements were made with Ni-filtered Cu-Kα radiation, and least-squares adjustment of the atomic parameters converged to a final R-value of 0.036. 13C NMR data are satisfactorily interpreted within terms of the structure. The mechanism of the transformation of arjungenin to tomentosic acid via formation of the 28→19 lactone is elucidated. The epimerisation of the 16β-OH group of cochalic acid to its 16α-isomer is also briefly described.Keywords
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