(1R,4S)-(+)-4-Hydroxy-2-cyclopentenyl acetate (CAS NO.: ), which is also known as 4--1,3-diol, monoacetate, (1R-cis)-, could be produced through the following synthetic routes.

A. cis-3,5-Diacetoxycyclopentene. A flame-dried, 100-mL, single-necked, round-bottomed flask is equipped with a serum cap, -coated magnetic stirring bar, and an 18-gauge needle attached to a dry source of argon vented through a mineral oil bubbler. The apparatus is flushed with argon and charged with 16.70 g (118 mmol) of (±)-cis-4-acetoxy-1-hydroxycyclopent-2-ene [(±)-1] and 20 mL of methylene chloride. To this stirred solution is added 8.81 g (129 mmol) of imidazole in one portion. When dissolution is complete, the reaction mixture is cooled to 0°C with the aid of an ice-water bath. (13.20 g, 12.20 mL, 129 mmol) is added dropwise over 5 min by means of an oven-dried syringe and needle. The cooling bath is removed and the reaction is allowed to stir at ambient temperature until judged complete by TLC analysis. The contents of the flask are transferred to a 250-mL separatory funnel and diluted with 60 mL of reagent grade ethyl ether. The contents of the separatory funnel are washed with 60 mL of ice-cold 1 N hydrochloric acid which results in noticeable removal of all color from the organic phase. The acidic aqueous phase is back-extracted with two 50-mL portions of ether. The combined organic phases are washed with a single 50-mL portion of saturated sodium bicarbonate solution followed by back-extraction of the aqueous phase with three 50-mL portions of ether (Note 6). The combined organic extracts are dried over anhydrous magnesium sulfate, filtered, and concentrated under rotary evaporation at 30 mm. The resulting viscous tan oil is distilled through a 10-cm Vigreux column to afford 20.9–21.1 g (96–98%) of cis-3,5-diacetoxycyclopentene (2) as a colorless liquid, bp 55–56°C at 0.1 mm.

B. (1R,4S)-(+)-4-Hydroxy-2-cyclopentenyl acetate. A rigorously clean 1-L Erlenmeyer flask, equipped with a 2-in. long Teflon-coated stirring bar, is charged with 320 mL of a 1.45 M sodium dihydrogen phosphate buffer concentrate. The solution is diluted to a final volume of 800 mL with the addition of 480 mL of glass-distilled water. To the gently stirred solution is added 78 mg of sodium azide followed by 18.6 mg (200 units/mg) of lyophilized electric eel acetyl cholinesterase (EEAC). The enzyme completely dissolves within 5 min after which time 16.01 g (87.0 mmol) of cis-3,5-diacetoxycyclopentene is added in one portion. A few extra mL of distilled water are used to facilitate a quantitative transfer of the diacetate. Parafilm is placed over the mouth of the flask and the two-phase system is allowed to stir at room temperature. The progress of the reaction is conveniently monitored by periodic TLC analysis. The reaction is terminated when only a trace of diacetate remains and the corresponding diol begins to appear. The aqueous phase is first extracted three times with 150-mL portions of ether followed by fifteen 150-mL extractions with a 1:1 mixture of ether/ethyl acetate. The organic extracts are combined, dried over anhydrous magnesium sulfate, and concentrated by rotory evaporation at 30 mm. The residue is passed through a 60-g plug of silica gel with approximately 750 mL of ether. Removal of the solvent by rotary evaporation followed by exposure to oil pump vacuum affords 11.32 g of nearly colorless material [mp 43–49°C (corrected)]. Vacuum distillation of the product through a short-path apparatus at 64°C/0.060 mm furnishes 10.64–10.76 g (86–87%, 96% e.e.) of colorless solid (+) hydroxy acetate 1 (mp 44.5–49.5°C (corrected), [α]D23 +62.9° (chloroform, c 1.465)). A sample recrystallized from 1:1 pentane/ether (approximately 5 mL/g) provides high purity (≥99% e.e.), colorless needles of 1 (mp 50.7–51.3°C (corrected), [α]_D23 +73.8° (chloroform, c 1.25) [lit. mp 49° − 51°C, [α]_D23 +68.0° (chloroform, c 1.64)]