Synthesis and analysis of the enantiomers of calmidazolium, and a 1H NMR demonstration of a chiral interaction with calmodulin

✍ Scribed by Andrew J. Edwards; Patricia J. Sweeney; David G. Reid; John M. Walker; Nabil Elshourbagy; Charles E. Egwuagu; James F. Young; Curtis L. Patton

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 454 KB
• Volume: 8
• Category: Article
• ISSN: 0899-0042
• DOI: 10.1002/(sici)1520-636x(1996)8:8<545::aid-chir2>3.0.co;2-8

✦ Synopsis

Calmidazolium 1R24571, 1-[ bis(4-chlorophenyl)methyl]-3-[2-(2,4dichloro-pheny1)-2- [ (2,4dichlorophenyl) methoxyl ethyl]-1H-imidazolium chloride} is a potent calmodulin inhibitor. This paper describes the synthesis and properties of the enantiomers of calmidazolium from the enantiomers of miconazole { 1 (N)-(2-(2,4-dichlorobenzyloxy)-2-(2,4-dichloropheny1))-ethyl imidazolel, prepared from the racemate by chiral preparative scale high performance liquid chromatography. Overlap between ligand and protein resonances in the aromatic region of the 'H NMR spectrum of the calmidazolium-calmodulin complexes has been obviated by preparation of the protein with all of its nine phenylalanine rings deuterated (Phe-d, calmodulin). This has been accomplished by the overexpression of calmodulin derived from Trypanosoma brucei rhodiesiense in E. coli in a medium supplemented with ring-deuterated phenylalanine. The kinetics of binding of each enantiomer are slow on the 'H NMR time scale as judged by the behaviour of the H2 resonance of Histidine-107, which is clearly visible under the sample conditions used. The aromatic spectral regions of the protein-bound (+) and (-) enantiomers contrast strikingly, reflecting differences in bound