Resolution of Binaphthols and Spirobiindanols Using Cholesterol Esterase

Cholesterol esterase (EC 3.1.1.13) catalyzes the hydrolysis of steroid, binaphthol, and spirobiindanol esters. The hydrolysis of binaphthol and spirobiindanol esters is enantiospecific and can be used to resolve these materials. Simple, synthetic-scale (200 g) procedures are detailed for the resolution of [1, 1-binaphthalene]-2, 2'-diol (1) and 2, 2, 3, 3'-tetrahydro-3, 3, 3, 3^'-tetramethyl-1, 1'-spirobi[1H-indene]-6, 6^'-diol (6). Resolution of 1 involved hydrolysis of the dipentanoate ester catalyzed by crude, inexpensive enzyme (bovine pancreas acetone powder) and yielded each enantiomer in >60% of theoretical yield with ≥99% enantiomeric purity. Similar resolution of 6 by hydrolysis of the dihexanoate ester yielded each enantiomer in >50% of theoretical yield with >95% enantiomeric purity. These resolutions involve two enzymic reactions: hydrolysis of the diester to the monoester followed by hydrolysis of the monoester to the diol. A theoretical analysis of such two-step resolutions suggests that two-step resolutions can yield products with higher enantiomeric purity than can single-step resolutions.