Methionine was found to be more efficient than formate, serine, bicarbonate, formaldehyde, or choline as a source of the C-28 methyl group of ergosterol in yeast (1). While transfer of an intact methyl group to carbon has not been previously recorded, oxidation of the methyl group of methionine to formate has been demonstrated and formate-Cl* has been shown to give rise to C-28 of ergosterol (2...