Cyano-13-epicobalamin (neovitamin B12) and its relatives

Abstract

An equilibration between cobinamide and neocobinamide with K≈ 1 occurs under highly acidic conditions. Similar equilibrations are reported with cobyric acid, other monocarboxylic acids, a dicarboxylic acid fraction, dehydrocobinamide, and with vitamin B₁₂ itself. The last process gives neovitamin B₁₂, which has been crystallised. Compounds of the neo-series resemble rather closely the analogous normal compounds, except in chiroptical properties.

Methanolysis of vitamin B₁₂ and of neocobinamide gives heptamethyl dicyanocobyrinate and heptamethyl dicyanoneocobyrinate, respectively, the mass spectra of which suggest that they are isomeric. This is confirmed by the X-ray analysis of neovitamin B₁₂ which shows it to be cyano-13-epicobalamin. In relation to the naturally derived corrinoids known so far, the neo-compounds are thus epimeric at C-13.