A demonstration of aldehyde-lactol tautomerism in gossypol by1H and13C NMR spectroscopy

CP/MAS spectroscopy in the determination of the tautomeric forms of gossypol, its Schiff bases and hydrazones in the solid state

“…If GOS were present in the lactol-lactol or ketol-ketol tautomeric forms, the signals of the C-11 or C-7 carbon atoms would have been observed in the 13 C CP/MAS spectra at about 103 or 170 ppm, respectively. [61,62] Furthermore, the multiple character of the C-11 carbon atom signal reflects the complex structure of GOS in solid state showing that the aldehyde groups form various inter-and intramolecular hydrogen bonds of slightly different strengths. The complex structure of GOS in the solid state is also obvious from the multiplicity of almost all other carbon atom signals in the CP/MAS spectrum ( Table 1).…”

Molecular and crystal structure of gossypol tetramethyl ether with an unknown solvate

“…In most solvents it is found in the aldehyde form. However, there are some reports that gossypol also exists in a pure lactol form (Reyes et al, 1986) or as a dynamic equilibrium mixture of the aldehyde and lactol forms in some highly polar solvents (Kamaev et al, 1979). In the structure described here, the title compound exists in the lactol form.…”

Crystal structure of bis-p-anizidinegossypol with an unknown solvate

“…Gossypol can exist in one of the following tautomeric forms: aldehyde, quinoid and lactol (Adams et al, 1960). In most solvents it is found in the aldehyde form; however, there are some reports that gossypol also exists in a pure lactol form (Reyes et al, 1986) or as a dynamic equilibrium mixture of aldehyde and lactol forms in some highly polar solvents (Kamaev et al, 1979). In the structure described here, the title compound is in the enamine or quinoid form.…”