(2S,3S)-2,6-Di­methyl­heptane-1,3-diol, the oxygenated side chain of 22(S)-hy­droxy­cholestrol, and its synthetic precursor (R)-4-benzyl-3-[(2R,3S)-3-hy­droxy-2,6-di­methyl­hepta­noyl]-1,3-oxazolidin-2-one

(2S,3S)-2,6-Di­methyl­heptane-1,3-diol, C₉H₂₀O₂, (I), was syn­thesized from the ketone (R)-4-benzyl-3-[(2R,3S)-3-hy­droxy-2,6-di­methyl­heptanoyl]-1,3-oxazolidin-2-one, C₁₉H₂₇NO₄, (II), containing C atoms of known chirality. In both structures, strong hydrogen bonds between the hy­droxy groups form tape motifs. The contribution from weaker C—H...O hydrogen bonds is much more evident in the structure of (II), which furthermore contains an example of a direct short Osp³...Csp² contact that represents a usually unrecognized type of inter­molecular inter­action.