A new route to polyoxygenate C and D rings of steroids by oxidation of a A(8,14)-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 o xidation with the urea-hydrogen peroxide adduct (UHP), the reactions of 5 a lpha -cholesta-8,14-dien-3 beta -y1 acetate 1 with the MTO-UHP system are p erformed in aprotic solvents. These oxidations are performed both at 0 degr eesC and 25 degreesC in CHCl3 or diethyl ether as solvent and in the presen ce of pyridine ligand. From the reaction of diene 1 in CHCl3 we isolate two new sterols, 9 beta -hydroxy-15-oxo-5 alpha -cholest-8(14)-en-3 beta -yl a cetate 3 and 9 alpha ,11 alpha ,15 alpha -trihydroxy-5 alpha -cholest-8(14) -en-3 beta -yl acetate 7. while oxidation in Et2O in the presence of pyridi ne ligand allows us to isolate the new epoxysteroid 9 alpha ,11 alpha -epox y-15 alpha -hydroxy-5 alpha -cholest-8(14)-en-3 beta -yl acetate 13. The st ructure of all new steroids is secured on the basis of chemical evidence an d interpretation of spectral data, which include H-H COSY, HMBC and NOESY e xperiments. These results represent a new and mild method for the functiona lization 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 st erol synthesis in animal cell culture systems.