A new route to polyoxygenate C and D rings of steroids by oxidation of a D8,14-diene steroid with the methyltrioxorhenium-H2O2-urea system

In order to find new ways of introducing oxygenated functions in the 15-, 9- and 11-position on steroid rings and at the same time test the reactivity of a conjugated diene steroid toward methyltrioxorhenium (MTO)-catalyzed oxidation with the urea-hydrogen peroxide adduct (UHP), the reactions of 5α-cholesta-8,14-dien-3β-yl acetate 1 with the MTO-UHP system are performed in aprotic solvents. These oxidations are performed both at 0 °C and 25 °C in CHCl3 or diethyl ether as solvent and in the presence of pyridine ligand. From the reaction of diene 1 in CHCl3 we isolate two new sterols, 9β-hydroxy-15-oxo-5α-cholest-8(14)-en-3β-yl acetate 3 and 9α,11α,15α-trihydroxy- 5α-cholest-8(14)-en-3β-yl acetate 7, while oxidation in Et2O in the presence of pyridine ligand allows us to isolate the new epoxysteroid 9α,11α-epoxy-15α-hydroxy-5α-cholest-8(14)-en- 3β-yl acetate 13. The structure of all new steroids is secured on the basis of chemical evidence and interpretation of spectral data, which include H-H COSY, HMBC and NOESY experiments. These results represent a new and mild method for the functionalization of C and D rings from an 8,14-diene steroid, to give 15-oxygenated sterols, a class of compounds remarkable for their inhibitory action on sterol synthesis in animal cell culture systems.