A. Racemic 1,1'-bi-2-naphthyl pentanoate. A suspension of 203 g (0.71 mol) of racemic 1,1'-bi-2-naphthol (Note 1) and 215 mL (1.54 mol) of triethylamine in 2 L of ethyl ether is stirred magnetically in a 4-L Erlenmeyer flask. Over a period of 20 min 185 mL (1.56 mol) of pentanoyl chloride is added (Note 2) and the suspension is stirred for an additional hour to ensure complete reaction (Note 3). The mixture is poured into a 6-L separatory funnel and washed twice with 2-L portions of aqueous 1 M sodium bicarbonate and once with a 2-L portion of water resulting in a clear yellow-orange ether solution.

B. (S)-(−)-1,1'-Bi-2-naphthol. In a 12-L, round-bottomed flask the above ether solution is diluted to 4 L with additional ethyl ether. A 5.0-mL aliquot of this solution is used to assay the enzyme (Note 4). The remaining ether solution is stirred using an overhead stirrer with 4 L of aqueous 0.1 M phosphate buffer (pH 7.5) containing 60 g of crude sodium taurocholate (Note 5). An opaque emulsion forms. The reaction is started by adding 2000 units of cholesterol esterase activity (100–150 g of bovine pancreas acetone powder, (Note 4)). Stirring is continued at ~25°C and the flask is stoppered to minimize evaporation of ether. The pH of the emulsion is measured occasionally and readjusted to 7.2 ± 0.3 by adding aqueous 1 M sodium hydroxide. Approximately 250 mL of base is consumed during the first 3 hr; an additional 400 mL is consumed over the next 20 hr. Although the consumption of base virtually ceases after 24 hr, stirring is continued for a total of 3 days (Note 6).

To break the emulsion 400 mL of ethanol is added and the mixture is transferred to separatory funnels and allowed to settle for 4 hr. Three layers form: at the top—a clear yellow ether phase, at the bottom—a brown aqueous phase and in between—an opaque emulsion layer. The brown aqueous layer is discarded. The emulsion layer (~1 L) is transferred to a flask and broken up by addition of 200 g of magnesium sulfate in portions. Heat is evolved, the ether boils and two layers form. This ether layer is combined with the first ether layer, dried over ~50 g of magnesium sulfate, filtered and concentrated by rotary evaporation to ~300 mL of an orange oil. Toluene (500 mL) is added and the solution cooled to 4°C overnight. Fine white crystals (70–71 g) are collected by filtration and washed twice with 20-mL portions of cold toluene (Note 7). The filtrate is concentrated to ~600 mL by rotary evaporation and cooled once again to 4°C. The additional 10 g of crystals which form are collected by filtration and washed twice with 20-mL portions of toluene. Recrystallization of the combined crystals from 375–400 mL of toluene yields 65–68 g (64–67%) of white crystals, mp 211–213.5°C; [α]_D19 −33.2 ± 0.8° (THF, c 0.2); >99% diol (see (Note 3)), >99.9% enantiomeric purity (Note 8).

C. (R)-(+)-1,1'-Bi-2-naphthol. Toluene in the above filtrate is removed by rotary evaporation, and the residue is recrystallized from methanol (500 mL) overnight at 4°C. Yellow crystals (125–141 g) form and are collected by filtration and washed twice with 20 mL of hexane. Recrystallization from 500 mL of methanol yields pure (R)-binaphthol dipentanoate [mp 63–65°C, 89–102 g, >99% ee (R), [α]_D19 +15.0 ± 0.3° (CHCl₃, c 0.4), (Note 9)]. If desired, an additional 25 g of dipentanoate can be isolated from the filtrate by column chromatography on 1 kg of silica gel eluted with methylene chloride followed by crystallization (Note 9).

The crystalline dipentanoate (89–102 g, 0.20 mol) is dissolved in 1 L of methanol containing 6.6 g (0.12 mol) of sodium methoxide. After 4 hr at room temperature, analysis of the solution by thin layer chromatography (Note 3) shows only traces of the mono- and diester. The solution is neutralized to pH <7 (test paper) with ~10 mL of concd hydrochloric acid. The solution is diluted with 1 L of 0.1 M phosphate buffer (pH 7), transferred to a 4-L separatory funnel and extracted with a mixture of 1 L of ethyl ether and 500 mL of toluene. The organic layer is washed with a 1-L portion of water, dried over magnesium sulfate, concentrated to 300 mL and cooled to 4°C. White crystals (48–64 g) separate and are collected by filtration and washed twice with 20-mL portions of cold toluene, mp 211–213.5°C; [α]_D19 +33.9 ± 0.2° (THF, c 0.2); 99% chemical purity (Note 3), >99% enantiomeric purity (Note 8).