G. W. Weaver, F. J. Leeper, A. R. Battersby, F. Blanche, D. Thibaut and L. Debussche
"Biosynthesis of Vitamin B12: the Site of Reduction of Precorrin-6x"
J. Chem. Soc., Chem. Commun.,1991, 976-979. Full Text
It is proved by deuterium labelling and NMR spectroscopy that a hydride equivalent from NADPH is transferred to C-19 of precorrin-6x as this intermediate is converted enzymically into hydrogenobyrinic acid.
Department of Chemistry
University of Cambridge