Biosynthesis of vitamin B12: use of specific 13C-labelling for structural studies on factor IV
Abstract
[1,10,20-13C3]Uro'gen III is unambiguously synthesised for enzymic conversion into precorrin-4 isolated after aerial oxidation as two epimers of Factor IV, the 13C NMR spectra of which rigorously confirm the presence of a C-1 acetyl group in precorrin-4; attachment of the fourth methyl group at C-17 of precorrin-4 is also confirmed by related 13C-labelling experiments.