An ent-kaurane diterpenoid from Isodon japonica var. glaucocalyx

The title compound, 14β-acet-oxy-7α-hydr-oxy-ent-kaur-16-ene-3,15-dione or glaucocalyxin B, C(22)H(30)O(5), a natural ent-kaurane diterpenoid, is composed of four rings with the expected cis and trans ring junctions. In the crystal structure, there are two mol-ecules in the asymmetric unit related by a noncrystallographic twofold screw axis, and ring A is disordered [ratio occupancies 0.829 (19):0.171 (19)], such that both chair and boat conformations are present, but with the boat conformation as the major component. In the crystal, mol-ecules are linked by inter-molecular O-H⋯O hydrogen bonds.