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

Abstract 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%).