Dimeric steroid formation in the color reaction of cholesterol.

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Abstract
The color reaction of cholesterol with trichloroacetic acid and hydrochloric acid (TCA-HCl) (1 : 1) was carried out in the presence of oxygen and/or hydrogen peroxide at a room temperature, and 3, 5-cholestadiene, 3, 3'-bis (3, 5-cholestadiene), cholesteryl chloride and cholesteryl trichloroacetate were isolated from the colored reaction mixture. From the observation of the absorption spectra, it was inferred that the absorption maximum at 560 or 563 nm should be ascribed to the carbocation formed by the protonation of 3, 3'-bis (3, 5-cholestadiene) in TCA-HCl (1 : 1). It was found that the dimerization was the main oxidative reaction in the present investigation, although it was suggested by many investigators that the formation of the monomeric cholestapolyenes should be the primary oxidation in the Liebermann-Burchard and the Zak reactions. From the result that the chlorinated steroids other than cholesteryl chloride were not acquired, it was assumed that cholesteryl chloride should be produced through the intermediate resulting from the dehydration of cholesterol in the acidic solution, and that 3, 3'-bis (3, 5-cholestadiene) also should be formed through this intermediate by an oxidative mechanism.

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