title: Spectroscopic studies and PM3 semiempirical calculations of Schiff bases of gossypol with L-amino acid methyl esters.
abstract: Three Schiff bases of racemic gossypol with L-amino acid methyl esters are synthesized and studied by FTIR and (1)H-NMR spectroscopy, and their structures are calculated by the PM3 semiempirical method. The Schiff bases in the study exist in the solid state and in solutions as enamine forms. The existence of diastereoisomers is very visible in the (1)H-NMR spectra. The amount of the diastereoisomers depends on the amount of time the solutions are rested in diffused light. The epimerization from D,L-isomer to L,L-isomer is very slow. The structures of the Schiff bases and the hydrogen bonds within these structures are discussed.
authors.affiliation: Department of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Przybylski
authors.forename: Bogumil
authors.initials: B
authors.lastname: Brzezinski
mesh_terms: D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry; D002725:Chloroform / Q000737:chemistry; D004952:Esters; D006072:Gossypol / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008432:Mathematical Computing; D008745:Methylation; D008958:Models, Molecular; D011522:Protons; D012545:Schiff Bases / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D004952:Esters; D011522:Protons; D012545:Schiff Bases; D002725:Chloroform; D006072:Gossypol