Acta Cryst. (2010). E66, o1531  [ doi:10.1107/S1600536810019483 ]

Acanthoic acid

S. Suwancharoen, W. Tommeurd, C. Phurat, N. Muangsin and S. Pornpakakul

Abstract: The title compound [systematic name: (1R,4aR,7S,8aS,10aS)-1,4a,7-trimethyl-7-vinyl-1,2,3,4,4a,6,7,8,8a,9,10,10a-dodecahydrophenanthrene-1-carboxylic acid], C₂₀H₃₀O₂, is a pimarane-type diterpene extracted from Croton oblongifolius. There are two independent molecules in the asymmetric unit. In both of these, the six-membered rings A, B and C adopt chair, boat and half-chair conformations, respectively. Rings A and B are trans-fused. The two molecules in the asymmetric unit form O-HO hydrogen-bonded R₂²(8) dimers. The absolute configuration was assigned on the basis of the published literature on analogous structures.

Online 5 June 2010

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