Absolute configuration of isovouacapenol C

The title compound, C(27)H(34)O(5) {systematic name: (4aR,5R,6R,6aS,7R,11aS,11bR)-4a,6-dihy-droxy-4,4,7,11b-tetra-methyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodeca-hydro-phenanthro[3,2-b]furan-5-yl benzoate}, is a cassane furan-oditerpene, which was isolated from the roots of Caesalpinia pulcherrima. The three cyclo-hexane rings are trans fused: two of these are in chair conformations with the third in a twisted half-chair conformation, whereas the furan ring is almost planar (r.m.s. deviation = 0.003 Å). An intra-molecular C-H⋯O inter-action generates an S(6) ring. The absolute configurations of the stereogenic centres at positions 4a, 5, 6, 6a, 7, 11a and 11b are R, R, R, S, R, S and R, respectively. In the crystal, mol-ecules are linked into infinite chains along [010] by O-H⋯O hydrogen bonds. C⋯O [3.306 (2)-3.347 (2) Å] short contacts and C-H⋯π inter-actions also occur.