title: Acanthoic Acid.
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-dodeca-hydro-phenanthrene-1-carb-oxy-lic acid], C(20)H(30)O(2), is a pimarane-type diterpene extracted from Croton oblongifolius. There are two independent mol-ecules 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 mol-ecules in the asymmetric unit form O-H⋯O hydrogen-bonded R(2) (2)(8) dimers. The absolute configuration was assigned on the basis of the published literature on analogous structures.
authors.affiliation: Research Centre of Bioorganic Chemistry, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Sunisa
authors.initials: S
authors.lastname: Suwancharoen
authors.forename: Wantanee
authors.initials: W
authors.lastname: Tommeurd
authors.forename: Chuttree
authors.initials: C
authors.lastname: Phurat
authors.forename: Nongnuj
authors.initials: N
authors.lastname: Muangsin
authors.forename: Surachai
authors.initials: S
authors.lastname: Pornpakakul