CHEMICAL STRUCTURE 



of A7-cholestenol to cholesterol (8). Oxidation of first one and 

 then of the second methyl group at C4 would once more yield 

 carboxylic acids which are susceptible to decarboxylation be- 

 cause of the double bond in /3,7 position. Admittedly other 



"COOH 



CH3 C2e 



C27 COOH 



Fig. 6. Scheme for the transformation of lanosterol to cholesterol. 



schemes could be and have been devised which are equally 

 plausible (see, for example, Mondon (16)). In fact the struc- 

 ture of zymosterol, a A8,24 cholestadienol present in small 

 amounts in yeast, could well be cited as an argument against the 

 above proposal that the double bond moves from the B/C junc- 

 tion to the 5,6 position in the course of the demethylation reac- 



487 



