Lanosterol was biosynthesized in pig liver homogenate from [4,8,12−14C3]farnesyl pyrophosphate and [4S-4−3H]NADPH through the intermediary formation of squalene labelled asymmetrically with 3H. The biosynthetic lanosterol, freed from labelled 24,25-dihydrolanosterol, which was also synthesized, was converted into 24,25-dihydrolanosteryl acetate and subjected to chemical degradations to locate the position(s) of the 3H label in the molecule. The ratio of 3H at C-11 to that at C-12 was found to be 1·28. Although a certain inequality of labelling was thus indicated, experimental uncertainties did not permit the conclusion that the asymmetrically labelled squalene might have been cyclized preferentially from one end.

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