Isolation and crystal structure of stigmast-4-ene-3β,6β-diol

The title compound (C29H50O2, M-r = 430.69) was isolated from the algae Halimeda xishaensis collected from the South China Sea. Its crystal structure was determined by single-crystal X-ray diffraction for the first time. The crystal belongs to orthorhombic, space group P2(1)2(1)2(1) with a = 8.1560(13), b = 10.7861(18), c = 29.973(5) Angstrom, V = 2636.8(8) Angstrom(3), Z = 4, D-c = 1.085 g/cm(3), F(000) = 960, mu(Mo-Kalpha) = 4.533 mm(-1), lambda = 0.71073 Angstrom, S = 1.061, (Deltarho)(max) 0.382 and (Deltarho)(min) = -0.244 e/Angstrom(3). The structure was refined to R = 0.0561 and wR = 0.1553 for 2711 observed reflections with I > 2sigma(I). X-ray diffraction analysis reveals that the title compound has two beta-OH groups, and the side chain is saturated. There exist two intermolecular hydrogen bonds between three molecules.