Cholestenone, formation

Solvent Effect on 5fl-Product Formation in the Hydrogenation of Cholestenone and Testosterone... 

In order to study the factors determining the regioselectivity of sodium borohydride reduction of a, -unsaturated ketones, reactions with 3-methylcyclohexenone, carvone and cholestenone were carried out in 2-propanol, diglyme, triglyme or pyridine. Mixtures of 1,2- and 1,4-reduction products were obtained in the alcoholic and ether solvents, whereas pure 1,4-reduction was observed in pyridine. Addition of triethylamine to NaBH4 in diglyme led to formation of triethylamine borine, EtsN BHs. Similarly, with pyridine, pyridine borine could be isolated, leading to exclusive 1,4-reductions. 

Metabolic inhibitors may fail even where no species selectivity is required. The antimetabolite A4)5-cholestenone, designed to inhibit cholesterol synthesis, illustrates this it blocks the conversion of desmosterol to cholesterol, the final step in this pathway (Fig. 4). The blockade of cholesterol formation, however,... 

The basis for all enzymatic cholesterol assays is the hydrolysis of cholesterol esters by cholesterol esterase (CEH, EC 3.1.1.13) to free cholesterol and fatty acids and the oxidation of free cholesterol to cholestenone by cholesterol oxidase (COD, EC 1.1.3.6) with concomitant oxygen consumption and hydrogen peroxide formation ... 

The reaction time and concentrations used depend on the reactants. Reaction is usually effected at 60°. Formation of condensation products from the ketones is largely repressed by working in inert solvents such as benzene, dioxan, and toluene. Aluminum isobutoxide, as well as the isopropoxide, has proved its value as metal alkoxide usually it is added to the reaction mixture in the proportion of 0.5 mole per mole of alcohol. Compounds containing nitrogen and halogen can also be oxidized by the Oppenauer method. Dehydrogenation of cholesterol to cholestenone will be described as an example 454... 

The mechanism of coprosterol formation in vivo. 1. Cholestenone as an intermediate. 

---