(25R)-6α-Hy-droxy-5α-spiro-stan-3β-yl tosyl-ate

The title steroid, C34H50O6S, is an inter-mediate on the synthetic route between diosgenin and brassinosteroids, which possess the A ring modified with the 2α,3α-diol functionality. The polycyclic spiro-stan system has the expected conformation, with six-membered rings adopting chair forms and the five-membered rings envelope forms (flap atoms are the methine C atom in the C/D-ring junction and the spiro C atom connecting rings E and F). The 3β-tosyl-ate group is oriented in such a way that S=O bonds are engaged in inter-molecular hydrogen bonds with O-H and C-H donors. Chains of mol-ecules are formed along [100] via O-H⋯O hydrogen bonds, and secondary weak C-H⋯O inter-actions connect two neighbouring chains in the [001] direction.