Alpha- and Beta-Diastereoisomers of Phenylcobalamin from Cobalt-Arylation with Diphenyliodonium Chloride

Abstract

Organometallic aryl-cobalamins are B12-derivatives featuring properties of potential ‘B12 antivitamins’. Herein, we describe a new method for the preparation of aryl-cobalamins using versatile diaryliodonium salts as arylation agents. Formate or sodium borohydride reduction of aquocobalamin in presence of diphenyliodonium chloride furnished Coβ-phenyl-cobalamin PhCbl in a roughly 3:1 to 1:1 ratio with its coordination isomer αPhCbl, a first representative ‘base-off’ Coα-aryl-cobalamin. The new structures were secured by detailed spectroscopic analysis, supplemented by an X-ray crystal structure analysis of PhCbl. Both types of coordination isomers of the aryl-cobalamins promise to be useful molecular tools in biomedical and biological studies.