Isolation and Crystal Structure of Stigmast-4-ene-3,6-diol

The title compound (C29H50O2, Mr = 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 P212121 with a = 8.1560(13), b = 10.7861(18), c = 29.973(5) ? V = 2636.8(8) 3, Z = 4, Dc = 1.085 g/cm3, F(000) = 960, (Mo-K? = 4.533 mm-1, ?= 0.71073 ? S = 1.061, (?max = 0.382 and (?min = 0.244 e/?. The structure was refined to R = 0.0561 and wR = 0.1553 for 2711 observed reflections with I > 2(I). X-ray diffraction analysis reveals that the title compound has two ?OH groups, and the side chain is saturated. There exist two intermolecular hydrogen bonds between three molecules.