title: Complete 1H, 13C and 15N NMR assignment of tirapazamine and related 1,2,4-benzotriazine N-oxides.
abstract: 1H, 13C and 15N NMR measurements (1D and 2D including 1H--15N gs-HMBC) have been carried out on 3-amino-1, 2,4-benzotriazine and a series of N-oxides and complete assignments established. N-Oxidation at any position resulted in large upfield shifts of the corresponding N-1 and N-2 resonances and downfield shifts for N-4 with the exception of the 3-amino-1,2,4-benzotriazine 1-oxide in which a small upfield shift of N-4 was observed. Density functional GIAO calculations of the 15N and 13C chemical shifts [B3LYP/6-31G(d)//B3LYP/6-311+G(2d,p)] gave good agreement with experimental values confirming the assignments. The combination of 13C and 15N NMR provides an unambiguous method for assigning the 1H and 13C resonances of N-oxides of 1,2,4-benzotriazines.
authors.affiliation: Auckland Cancer Society Research Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
authors.forename: Maruta
authors.initials: M
authors.lastname: Boyd
authors.forename: Michael P
authors.initials: MP
authors.lastname: Hay
authors.forename: Peter D W
authors.initials: PD
authors.lastname: Boyd
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis; D006859:Hydrogen / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure; D009587:Nitrogen Isotopes / Q000032:analysis; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D000077704:Tirapazamine; D014227:Triazines / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D010087:Oxides; D014227:Triazines; D000077704:Tirapazamine; D006859:Hydrogen