Reactions of the carbon-cobalt bond of alkylcobalamins. A reversible dissociation of the carbon-cobalt bond.

The cobamide coenzymes’ are unstable in the presence of alkaline cyanide. This decomposition by cyanide has been envisaged as a nucleophilic displacement reaction which gives rise to dicyanocobalamin, adenine, and the cyanohydrins of 2,3dihydroxy-A4-pentenal (1, 2). In the case of the simple alkylcobalamins, cyanide decomposition proceeds very slowly or not at all, presumably because the alkyl carbanion is a poor leaving group (2). However, Hogenkamp, Rush, and Swenson (3) recently reported that alkylcobalamins, which contain cyanoethyl and methoxycarbonylethyl functions, are readily decomposed by