meso-Halogenated nitrosylcobalamins: Formation and aerobic stability

Abstract

Here, we report the results of the investigation of reactions between brominated and chlorinated at the C10 position of corrin cyano- (CNCbl-Hal, Hal = Br, Cl) and aquacobalamins (H2OCbl-Hal) and Angeli’s salt (AS). The reactions involving H2OCbl-Hal and AS proceed via two parallel routes, i.e., reactions between H2OCbl-Hal or HOCbl-Hal and HNO generated upon decomposition of AS and between H2OCbl-Hal and AS, and generate corresponding nitrosylcobalamins (NOCbl-Hal). In contrast to the process involving unmodified CNCbl, the reactions between CNCbl-Hal and HNO can be used to produce NOCbl-Hal, which can be explained by the labilization of the axial Co(III)-N[Formula: see text] bond upon meso-halogenation facilitating the reaction between HNO and the lower axial position of CNCbl-Hal. We indicated that the process is initiated by the relatively slow formation of CNCbl-Hal species with dissociated 5,6-dimethylbenzimidazole nucleotide and further rapid binding of HNO by Co(III) ion. Produced NOCbl-Hal reacts with dioxygen significantly slower than unmodified NOCbl and can be recommended for further investigation of their biological and medicinal properties.