18-Substituted steroids. Part 13. Improved preparation of the metabolites of aldosterone reduced in ring A

Abstract

Protection of the side-chain of aldosterone as the 21-t-butyldimethylsilyl (TBDMS) ether was also found to mask the 20-oxo function, by effectively locking the tautomeric structure of aldosterone into its 11,18:18,20-diepoxy form. Catalytic hydrogenation of aldosterone 21-TBDMS ether gave the 5α- or the 5β-dihydro derivative depending on the choice of solvent. Subsequent reduction of the carbonyl group at C-3, with either ‘K-selectride’ to form the 3-axial alcohol or lithium tri-t-butoxyaluminium hydride to form the 3-equatorial alcohol, was found to proceed without attack on the side-chain, to give convenient routes to the four isomeric tetrahydroaldosterones.