Lipase-catalyzed stereoselective acylation of [1,1'-binaphthyl]-2,2'-diol and deacylation of its esters in an organic solvent.

Abstract

A kinetic resolution of [1, 1-binaphthyl]-2, 2'-diol (binaphthol) and its esters was first accomplished by lipase-catalyzed transesterification in an organic solvent. Acylation of binaphthol with enol esters in diisopropyl ether-acetone (9:1, v/v) gave solely (R)-2-acyloxy-2'-hydroxy-1, 1'-binaphthyl (binaphthyl monoesters) having 90 - 95 % optical purities. The unreacted binaphthol, which was also recovered in high chemical yields, was the S enantiomer with 69-89% e.e. On the other hand, the lipase-catalyzed deacylation or alcoholysis of racemic binaphthyl monoesters gave (S)-monoesters and (R)-binaphthol in high chemical and optical yields (>90% e.e.). In deacylation, the reaction period was much shortened by introducing the more electronegative chlorine atom into the acetyl group of the substrate.