1H, 13C and 15N NMR assignments of phenazopyridine derivatives.
Phenazopyridine hydrochloride (1), a drug in clinical use for many decades, and some derivatives were studied by one- and two-dimensional (1)H, (13)C and (15)N NMR methodology. The assignments, combined with DFT calculations, reveal that the preferred protonation site of the drug is the pyridine ring nitrogen atom. The chemoselective acetylation of phenazopyridine (2) and its influence on the polarization of the azo nitrogen atoms were evidenced by the (15)N NMR spectra. Molecular calculations of the phenazopyridines 2-4 show that the pyridine and phenyl groups are oriented in an antiperiplanar conformation with intramolecular hydrogen bonding between the N-b atom and the C-2 amino group preserving the E-azo stereochemistry.
Burgueño-Tapia
Eleuterio
E
Departamento de Química, Unidad Profesional Interdisciplinaria de Biotecnología, Instituto Politécnico Nacional, Av. Acueducto s/n, La Laguna Ticomán, México D.F., 07340 Mexico.
Mora-Pérez
Yolanda
Y
Morales-Ríos
Martha S
MS
Joseph-Nathan
Pedro
P
D002247:Carbon Isotopes; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D008968:Molecular Conformation; D009587:Nitrogen Isotopes; D010621:Phenazopyridine / Q000032:analysis* / Q000737:chemistry* / Q000592:standards; D011522:Protons; D012016:Reference Values
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D011522:Protons; D010621:Phenazopyridine