LaPlanche, Laurine A.
M.S. (Master of Science)
Department of Chemistry
Verapamil hydrochloride; Antihistamines; Pheniramine maleate; Nuclear magnetic resonance spectroscopy; Calcium--Antagonists
Pheniramine maleate is the antihistamine component of Dristan nasal spray. ‘H and 13C chemical shift assignments were obtained using 2-D NMR spectroscopy. This work provides the first 13C chemical shift assignments for this molecule. In order to maximize peak separation in the 'H spectrum, these experiments were performed in DMSO-d6. A combination of 13C DEPT (Distortionless Enhancement by Polarization Transfer) plus one-bond and long-range 2-D heteronuclear NMR experiments allowed for the assignments of all l3C peaks in the molecule. A double-quantum filtered COSY (correlated SpectroscopY) experiment was performed for proton-proton correlation. Trends in the chemical shifts were also observed in D20 under protonation (pH = 2.0 to pH = 8.7). A change in conformation is postulated as the molecule is protonated: the monoprotonated ion in DMSO-d6 is believed to be in a folded conformation, while the diprotonated ion (pH =2.0) is believed to be in an extended conformation. Verapamil hydrochloride is a calcium channel antagonist used to treat cardiac dysrhymias. Under conditions of slow proton exchange, the hydrochloride possesses two chiral centers and is therefore diastereomeric. 2-D NMR was used to assign the 'H and 13C chemical shifts at room temperature. 2-D COSY and double quantum filtered COSY experiments were performed for the proton-proton correlation and assignments. One-bond and long-range 2-D heteronuclear NMR experiments were used to assign the resonances in the 13C spectrum. Deprotonation of the amine nitrogen was performed by adding small amounts of triethylamine to verapamil hydrochloride in a solution of CD2C12, which was the best solvent for peak separation at room temperature. However, (CDC12)2 (1,1,2,2- tetrachloroethane-d2) was used for high temperature studies. High temperature NMR studies were performed in order to increase the rate of exchange of the amine proton and increase the rotation about the bonds in the alkyl portions of the molecule, thus simplifing the spectra.
Dingmann, Michael G., "A study of pheniramine maleate and verapamil hydrochloride by 2-D NMR techniques" (1994). Graduate Research Theses & Dissertations. 662.
ix, 111 pages
Northern Illinois University
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