Schiff bases of gossypol: an NMR and DFT study.
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.
That
Quang Ton
QT
University of Natural Sciences, National University of HoChiMinh City, Vietnam.
Nguyen
Kim Phi Phung
KP
Hansen
Poul Erik
PE
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
D002247:Carbon Isotopes; D011522:Protons; D012545:Schiff Bases; D003903:Deuterium; D006072:Gossypol