Oxidative fragmentations of 5-hydroxy-1-oxo-5alpha-cholestan-3beta-yl acetate

5-Hydroxy-1-oxo-5a-cholestan-3b-yl acetate (11) was prepared in 5 steps starting from (E)-3b-acetoxy-5,10-seco-1(10)-cholesten-5-one (6). Treatment of the 1-oxo-5-hydroxy derivative 11 with lead tetraacetate (LTA) (under thermal or hypoiodite conditions) or with mercuric oxide/iodine (HgO/I2) reagent resulted in the oxidative b-fragmentation of the C(5) C(10) bond affording 1,5-dioxo-5,10-secocholest-10(19)-en-3b-yl acetate (12), in different yields, depending on the reagent. Also the stereochemistry of the 1b,6b-cyclization product 13, formed by transannular cyclization of the 1,5-diketone 12 on silica gel, is discussed in this work.