Lanosterol demethylation, scheme

Scheme 12.5 Demethylation of lanosterol (16) to 4,4-dimethyl-5a-cholesta-8,14,24-diene-3 3-ol (19) catalyzed by lanosterol 14a-demethylase (CYP51).

Another example for the cleavage of C-C bonds via multiple substrate oxidations is the demethylation of lanosterol to a precursor of cholesterol, 4,4-dimethyl-5a-cholesta-8,14,24-diene-3p-ol, catalyzed by a lanosterol 14a-demethylase (CYP51) [39]. The mechanism includes three steps and proceeds via initial hydroxylation of the C14 methyl group (corresponds to C32 hydroxylation), followed by further oxidation of the alcohol to the aldehyde. Finally, acyl cleavage occurs, leading to the formation of a double bond in the steroid (Scheme 5.8). 

Scheme 5.8 Demethylation of lanosterol via multistep oxidations catalyzed by CYP51.

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