336 IV. WAXES, HIGHER ALCOHOLS, ETC. 



r The second double bond can likewise be introduced into the sterol nucleus 

 at the 7:8 position by treatment of the acetate with iV-bromosuccini- 

 mide.^^^ Bromine enters the sterol nucleus at position 7. It may be dis- 

 lodged from this position by treatment with dimethylaniline, as a result of 

 which 7-dehydrocholesterol originates. Yields as high as 50% may result. ^^* 



Cholesterol forms a series of unstable addition products with the fatty 

 acids (acetic, butyric, palmitic, stearic, and oleic), as well as with oxalic 

 acid. It also yields an addition product with saponin. 



On oxidation, cholesterol forms a series of derivatives which vary with 

 the severity of the oxidizing agent. Thus, on mild oxidation with cupric 

 oxide, it is converted to the ketone cholestenone, in which the double bond 



u CHj CH3 



H I * I ' 



C — C — CHj— CHaCH^-CH— CH« 

 I H 



CH, 



Cholestenone 



has shifted from the 5:6 to the 4:5 position. On more violent oxidation 

 with chromic acid, potassium permanganate, or hydrogen peroxide, decom- 

 position products result which have been useful in establishing the struc- 

 tural configuration of the sterol nucleus. As mentioned earlier, dehydro- 

 genation with a selenium catalyst yields chrysene,^^^ or the so-called Diels' 

 hydrocarbon. ^^^•^•'^ Thermal decomposition products likewise include 

 naphthalene as well as small amounts of styrene.*^^ 



Stereoisomerism is a most important property of cholesterol and related 

 sterols. The metabolism of such stereoisomeric fonns is quite unique, and 

 varies with the compound in question. Moreover, the response of the 

 sterol to precipitation reactions is closely related to the stereochemical con- 

 figuration. The most important point of asymmetry in cholesterol itself is 

 at C3, while a second important focal point for such cholesterol derivatives 

 as cholestenone or dihydrocholesterol obtains at position 5. The latter 

 carbon is not an asymmetric one in cholesterol, because of the double bond 



1" H. B. Henhest, E. R. H. Jonos, .\. E. Bide, II. W. Peeveis, and P. A. Wilkinson, 



Nature, 158, 169 (1946). 



"* E. F. Week, Personal communication. 



i»» H. Fischer and A. Triebs, Ann., U6, 241-259 (1925). 



