Optically active BINOL can also be obtained from racemic BINOL by optical resolution. In one method, the alkaloid N-benzylcinchonidinium chloride forms a crystalline inclusion compound. The inclusion compound of the ("S")-enantiomer is soluble in acetonitrile but that of the ("R")-enantiomer is not. In another method BINOL is esterified with pentanoyl chloride. The enzyme cholesterol esterase hydrolyses the ("S")-diester but not the ("R")-diester. The ("R")-dipentanoate is hydrolysed in a second step with sodium methoxide. The third method employs HPLC with chiral stationary phases.