Further study on oxidation of pseudosapogenins

Abstract

6β-Methoxy-3α,5-cyclo-5α-furost-20(22)-ene (4) and its 26-tosyloxy derivative (3) were oxidized with m-chloroperoxybenzoic acid, dimethyldioxirane and osmium tetroxide. The reaction of 4 with MCPBA yielded the allylic alcohol 6, the α,β-unsaturated ketone 7 and the α-hydroxy-lactone 8. Similar reaction of 3 carried out in a buffered medium led to the products 9 and 10 with the C20-C22 bond cleaved. The reaction of the same compound with dimethyldioxirane afforded the allylic alcohol 5. The oxidation of pseudosapogenins with OsO 4 gave dihydroxylation products 11 and 12.

Synthesis of the Antiproliferative Agent Hippuristanol and Its Analogues via Suárez Cyclizations and Hg(II)-Catalyzed Spiroketalizations

“…A clean and stereospecific epoxidation of 21 using dimethyldioxirane afforded epoxide 22 . The same transformation using m CPBA proved unfruitful, leading to complete degradation of the E ring . Regioselective reductive opening of epoxide 22 using NaCNBH 3 in AcOH produced alcohol 23 as a mixture of C22-epimers.…”