Carbon-13 nuclear magnetic resonance studies of cyanocobalamin and several of its analogues.

The carbon-13 nuclear magnetic resonance spectrum of cyanocobalamin in aqueous solution has been interpreted. The assignments are based on the earlier biosynthetic studies with carbon-13-enriched precursors and on the present systematic analysis of the spectra of cyanocobalamin, cyanocobalamin lactone, cyanocobalamin lactam, cyanoepicobalamin, and several cyanocobalaminmonocarboxylic acids. The interpretation of the spectrum of cyanocobalamin greatly simplifies the structure determination of new corrinoids and should prove very helpful in future studies of these compounds. The structures of two cyanocobalamindicarboxylic acids and a cyanocobalaminmonocarboxylic acid lactone have been determined by comparing their carbon-13 magnetic resonance spectra with that of cyanocobalamin.