REACTION OF RUO4 WITH CARBON-CARBON DOUBLE-BONDS - PART 8 - REACTION OF 7,8-DIDEHYDROCHOLESTERYL ACETATE AND CHOLESTERYL ACETATE WITH RUO4 AND OSO4 - A COMPARATIVE VIEW

The title reactions have been studied. The first formed compound from the oxidation of 7,8-didehydrocholesteryl acetate with RuO4 performed in acetone-water (5:1), both at room temperature and -70 degrees C, is the ruthenium(VI) diester 5. In mild acidic conditions compound 5 con verts into the isomeric compound 6 that in turn is in equilibrium in t he same conditions with a third isomeric ruthenium(VI) diester, 2, a c ompound previously isolated from the same oxidative process conducted at -70 degrees C. The structural relationship between the isomeric com pounds 2, 5 and 6 has been established by careful spectral analyses an d comparison of their NMR properties with those exhibited by the osmiu m-containing analogues (7 and 8) of the ruthenate esters 2 and 5, synt hesized by reaction of 7,8-didehydrocholesteryl acetate with OsO, in d ioxane. The RuO4 oxidation of cholesteryl acetate at room temperature also furnishes two ruthenium(vr) diesters (9 and 10) structurally anal ogous to compounds 2 and 5. NMR evidence is reported that the Ru=O and Os=O groups possess similar magnetic anisotropy. The isomerization pr ocess involving the ruthenate esters of 7,8-didehydrocholesteryl aceta te has also been studied by H-1 NMR spectroscopy and is briefly discus sed.