Rapid access to a series of calcitriol analogues with restricted side chain conformation

Crystal structure of (1R,3aR,7aR)-1-{(S)-1-[(2R,5S)-5-(3-hy-droxy-pentan-3-yl)tetra-hydro-furan-2-yl]eth-yl}-7a-methyl-2,3,3a,4,5,6,7,7a-octa-hydro-1H-inden-4-one

The title compound, C21H36O3, contains an oxolane ring, and six defined stereocentres and may serve as a useful synthon for the synthesis of calcitriol analogues. The configurations of the chiral C atoms of the side chain were unambiguously established in the refinement. In the crystal, C-H⋯O and extremely weak O-H⋯O hydrogen bonds arising from the sterically hindered alcohol group link the mol-ecules into a three-dimensional network.