F. Blanche, M. Kodera, M. Couder, F. J. Leeper, D. Thibaut and A. R. Battersby
"Biosynthesis of Vitamin B12: Use of a Single 13C Label in the Macrocycle to Confirm C-11 Methylation in Precorrin-6x"
J. Chem. Soc., Chem. Commun.,1992, 138-139. Full Text
[11-13C]Uro'gen III is unambiguously synthesised for enzymic conversion into precorrin-6x which as its octamethyl ester gives a 13C NMR spectrum confirming the presence of a C-11 methyl group.
Department of Chemistry
University of Cambridge