Biosynthesis of vitamin B12: when is the 12β-methyl group of the vitamin generated by acetate decarboxylation?
Abstract
The 12-methyl analogue (13) of the aromatised form of precorrin-3(5) has been prepared by enzymic C-methylation of 12-decarboxy-uro'gen-III (2) and is used for incorporation experiments which indicate that decarboxylation of the 12-acetate residue in B12-biosynthesis occurs after C-17 methylation.