Redox-Neutral Syntheses and Electrochemical Studies of 10-Bromo-Substituted Light-Stable Antivitamin B12 Candidates |
| |
Authors: | Christopher Brenig Leila Mosberger Katja Baumann Olivier Blacque Felix Zelder |
| |
Affiliation: | Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland |
| |
Abstract: | This publication describes the straightforward and redox-neutral synthesis of 10-bromophenylethynylcobalamin and its facile conversion to 10-bromoaquacobalamin. In this approach, the phenylethynyl ligand acts as convenient light-stable protecting group that is removed in quantitative yield under acidic conditions. The proteolytic cleavage at pH 2.0 was studied under pseudo-first-order conditions and is 1.5 times slower than that of phenylethynylcobalamin with a hydrogen instead of a bromine at C(10). Preliminary electrochemical studies of organometallic ethynyl-Cbls (Cbl=cobalamin) are reported for the first time. A reduction potential of −0.94 V vs. Ag/AgCl was determined for the CoIII/CoI reduction of 10-bromophenylethynylcobalamin. The positive potential shift of 180 mV compared to phenylethynylcobalamin is in agreement with earlier electrochemical studies of related cyanocobalamins. |
| |
Keywords: | antivitamin aquacobalamin cis-effect cobalamins electrochemistry vitamin B12 |
|