324 IV. WAXES, HIGHER ALCOHOLS, ETC. 



toad poisons (bufotoxin, bufotalin, and cinobufagin), as well as from car- 

 diac glycosides and sapogenins: 



Diels' hydrocarbon (CisHic) 



Other information useful in establishing the structural relationships of 

 cholesterol can now be interpreted. For example, it had been known that 

 the molcule contained a double bond which could take up halogens. The 

 double bond and the hydroxyl group were on two rings which were adja- 

 cent since, on oxidation, a tetracarboxylic acid was obtained with the same 

 number of carbons as cholesterol. ^^^-^^^ From the chemical properties of 

 this acid and of numerous oxidation products, it could be deduced that the 

 two rings, A and B, were condensed with each other, and that the unsatu- 

 rated linkage was in a /3,7-position to the hydroxyl group. 



The structure of the side chain of cholesterol had been well known for a 

 number of years after Windaus and Resau^*'^ demonstrated, in 1913, that 

 methyl heptanone, (CH3)2CH • CH2 • CH2 • CO • CH3, originates on energetic 

 oxidation of this sterol. This would indicate that the ketone group (C20) is 

 the site of a combination of the side chain with the cyclopentenophenan- 

 threne ring, while the adjacent methyl group obviously represents a side 

 chain attached at C20. The rest of the aliphatic chain is apparently un- 

 altered by this treatment. 



The sterols are quite similar in certain general physical properties. They 

 are white crystalline solids which are insoluble in water, but which readily 

 dissolve in fats and fat solvents. For the most part, they are optically 

 active. They contain 26 to 30 carbons, and all have four carbocyclic rings. 

 The side chain is invariably attached to the fourth ring in position 17. 

 They have a single secondary alcohol group on the first ring (position 3) 

 which may be esterified in the presence of acids or oxidized to a ketone. 

 Bile acids and other steroids, such as the adrenocortical and sex hormones, 

 may have additional hydroxyl groups on the cyclopentenophenanthrene 



i« A. Windaus and I. Stein, Ber., 37, 3699-3708 (1904). 

 i« A. Windaus and M. Deppe, Ber., 66, 1563-1.5G5 (1933). 

 »« A. Windaus and C. Resau, Ber., 46, 1246-1248 (1913). 



