Absolute configuration of vouaca­pen-5α-ol

The title compound, C(20)H(30)O(2), {systematic name: (4aR,6aS,7R,11aS,11bR)-4,4,7,11b-tetra­methyl-1,2,3,4,4a,5,6,6a,7,11,11a,11b-dodeca­hydro­phenanthro[3,2-b]furan-4a-ol}, is a cas­sane furan­oditerpene which was isolated from the roots of Caesalpinia pulcherrima. The absolute configurations at positions 4a, 6a, 7, 11a and 11b are R, S, R, S and R, respectively. The mol­ecule has four-fused rings consisting of three cyclo­hexane rings and one furan ring. The three cyclo­hexane rings are trans-fused. Two cyclo­hexane rings are in chair conformations, while the third is in an envelope conformation. In the crystal structure, the mol­ecules are linked by inter­molecular O—H⋯O hydrogen bonds into a zigzag chain along the a axis. A short O⋯O contact [3.0398 (14) Å] is also present.