Synthesis and characterization of halogenated derivatives of ionophore A23187

INOR 583

Trevor K. Ellis, tellis@ou.edu, Kendra L. Cox, kcox@ou.edu, Douglas Powell, and Richard W. Taylor, rwtaylor@ou.edu. Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Room 208, Norman, OK 73019
Antibiotic A23187 is a member of the polyether carboxylic acid class of ionophores and transports divalent metal ions selectively relative to monovalent cations. The transport selectivity at pH 7.0 in palmitoyloleoylphosphatidylcholine (POPC) vesicles is: Zn>Mn>Ca>Co>Ni>Sr. Halogenation of the benzoxazole and/or pyrrole moieties alters the complexation and transport properties of the ionophore. For example, the derivative with chlorine at the 4 position of the benzoxazole group, 4-ClA23187, shows the following transport selectivity sequence at pH 7.0 in POPC vesicles: Zn>Cd>Mn>Co>>Ni>>Ca~Sr. Introduction of two bromine atoms to the pyrrole ring yields 23,24-Br2A23187. As a result the pKa of the pyrrole proton is lowered to 11.7 in 80% CH3OH-H2O and the dibromo derivative can act as a dianionic ligand. Titration studies with divalent metal ions show that the ML complex is formed preferentially with Cd2+, Zn2+, and Ni2+, while Ca2+ and Mg2+ form both ML and ML2 type complexes.
 

Characterization and Applications of Coordination Compounds
7:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Sci-Mix

Division of Inorganic Chemistry

The 234th ACS National Meeting, Boston, MA, August 19-23, 2007