A,<1, -Cholestenyl acetate

Diagnosis of unsaturation types. A -Cholestenyl acetate is oxidized by selenium dioxide in acetic acid-benzene to give 7a-acetoxy-A -cholestene (2), probably by allylic hydroxylation at C14, allylic rearrangement, and acetylation. Since oxidation occurs readily at room temperature whereas cholesterol is attacked only at 55-60°, the reaction can be used to detect small amounts of A -cholestenol... 

Steroid ketoxides of types (1) and (3), both of which result on dichromate oxidation of A -cholestenyl acetate, are reduced by zinc dust and acetic acid to the corresponding conjugated ketones, (2) and (4). ... 

The nature of the product resulting from selenium dioxide oxidation of an ene or diene depends upon the specific structure and the reaction conditions. Oxidation of A -cholestenyl acetate (1) in acetic acid gives the A -7Q..acetoxy compound (2) oxidation in ethanol benzene gives the A >-7a-ethyl ether. In other instances an ene gives a diene, a diene gives a triene. 

Dehydration. Wintersteiner and Moore " effected dehydration of 3/3-acetoxy-cholestane-7a-ol by reaction with tosyl chloride in refluxing pyridine and obtained a mixture of stenyl acetates rich in the A -isomer and convertible into pure A "" )-cholestenyl acetate on catalytic rearrangement. 

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