Conversion of ruscogenin into 1α- and 1β hydroxycholesterol derivatives. Structure elucidation by computer assisted analysis of their lanthanide-induced nmr shifts

The chemistry of ruscogenin (1) was studied since its structural features qualify it to serve as a potential starting material for 1-hydroxy vitamin D analogs. Ruscogenin was oxidized to the 1-oxo-derivative 2 which was reduced to a mixture of ruscogenin (1) and 1-epiruscogenin (3). Both 1 and 3 were converted by Clemmensen reduction to the respective tetrols 12 and 21, which were further reduced to the triols 15 and 25 and diols 16 and 24 by consecutive treatment with p- toluenesulfonyl chloride and LAH. The reduction of triol 15 to diol 20 was achieved by selective benzoylation of positions 1 and 3, and mesylation of position 16 followed by LAH reduction. The utility of the shift reagent Eu(dpm)₃ to determine the structures of the products was studied. It was shown that the shifts induced are characteristic of the position and orientation of the OH groups, and can facilitate the elucidation of the structures of hydroxylated steroids.