An expedient route for the practical preparation of optically active (-)-gossypol

A simple and practical procedure has been developed for the resolution of racemic gossypol. The commercially available L-amino acid esters have been employed as the resolving agents with the L-tryptophan methyl ester (L-Trp-OMe) as the best reagent of choice. The individual diastereoisomeric gossypol adducts derived from L-Trp-OMe are readily separated by a simple filtration step to give the (-)-diastereoisomeric adduct, and its (+)-diastereoisomeric adduct can be easily obtained by simple evaporation of the mother liquor. Acid hydrolysis of the separated adduct gave (-)-gossypol and (+)-gossypol, respectively, in high chemical yields (quantitatively) and in high enantiomeric excesses (> 95%). (c) 2007 Elsevier Ltd. All rights reserved.