title: Schiff bases of gossypol: an NMR and DFT study.
abstract: Schiff bases of gossypol with benzylamine, methylamine, 4-aminoacetophenone and 4-fluoroaniline have been synthesized and characterized by NMR spectroscopy. All the Schiff bases of gossypol are in the enamine form according to (3)J(HC,NH) and (1)J(N,H) coupling constants. The spectra are basically unchanged by change of solvent (CD(2)Cl(2), THF-d(8) and CD(3)OD) and by variation of temperature. For the derivative of benzylamine, deuterium isotope effects on (13)C chemical shifts are determined. They support strongly the enamine form and serve as a reference for other tautomeric Schiff bases. Structures and NMR nuclear shieldings of model compounds (the second monomer is replaced by a 2-hydroxybenzene ring) have been calculated by density functional theory (DFT) methods. A good correlation is observed between calculated (13)C nuclear shieldings of the enamine form and observed (13)C chemical shifts.
authors.affiliation: University of Natural Sciences, National University of HoChiMinh City, Vietnam.
authors.forename: Quang Ton
authors.initials: QT
authors.lastname: That
authors.forename: Kim Phi Phung
authors.initials: KP
authors.lastname: Nguyen
authors.forename: Poul Erik
authors.initials: PE
authors.lastname: Hansen
mesh_terms: D002247:Carbon Isotopes; D003903:Deuterium / Q000737:chemistry; D006072:Gossypol / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods* / Q000592:standards; D015394:Molecular Structure; D011522:Protons; D012015:Reference Standards; D012545:Schiff Bases / Q000138:chemical synthesis / Q000737:chemistry*; D013696:Temperature
chemical_list: D002247:Carbon Isotopes; D011522:Protons; D012545:Schiff Bases; D003903:Deuterium; D006072:Gossypol