H-1-NMR STUDIES OF GOSSYPOL AND ITS COMPLEXES WITH SOME ORGANIC-COMPOUNDS

The 1H NMR spectra of gossypol and its complexes with some organic compounds in various solvents have been analyzed. In CDCl3 solution gossypol exists as the (±) aldehyde tautomer. In other solvents, aldehyde and lactol tautomers are in equilibrium, depending on the nucleophilicity of solvent (B). In the case of complexes of gossypol with organic compounds, the equilibrium is shifted to the aldehyde form, and the (±) diastereoisomers were observed in the 1H NMR spectrum due to asymmetric nonspecific interactions. Two types of tetrabutylammonium complexes of gossypol, 2:1 and 4:1 have been prepared. The spectrum of the 2:1 salt points to a very complex equilibrium in solution without a ketol tautomer. In this case a new type of intramolecular hydrogen bond is formed. Ketol is the main tautomeric form of the 4:1 salt, which shows a very strong intermolecular OHO- type hydrogen bond. © 1990.