(-)-(E,S)-3-(Benzyloxy)-1-butenyl phenyl sulfone (CAS no.: ), which is also known as , [[[1-methyl-3-(phenylsulfonyl)-2-propenyl]oxy]methyl]-, [S-(E)]-, could be made from the following synthesis routes.

A. (-)-(S)-Ethyl 2-(benzyloxy)propanoate. As described in ref. 3, a flame-dried, 500-mL Schlenk flask equipped with a magnetic stirring bar, rubber septum, and an argon balloon is charged with 11.8 g (100 mmol) of (S)-ethyl 2-hydroxypropanoate [(S)-ethyl lactate] and 50.9 g (200 mmol) of O-benzyl-2,2,2-trichloroacetimidate. The reagents are dissolved in 250 mL of a mixture of anhydrous cyclohexane and anhydrous dichloromethane (7:1 v/v) under an atmosphere of argon. Neat trifluoromethanesulfonic acid (0.4 mL, 4.53 mmol) is added dropwise by means of a syringe while the mixture is stirred rapidly. The reaction mixture is stirred for 48 to 60 hr at room temperature and subsequently diluted with water (100 mL) and hexane (300 mL). Stirring is continued for an additional 3 hr at room temperature. The precipitated colorless trichloroacetamide is filtered off by means of a Büchner funnel. The aqueous phase is separated and extracted three times with 50-mL portions of hexane . The combined organic extracts are washed with 50 mL of aqueous saturated sodium bicarbonate (NaHCO₃) solution and finally with 50 mL of aqueous saturated sodium chloride (NaCl) solution. After drying over magnesium sulfate (MgSO₄), filtration and removal of the solvents under reduced pressure by means of a rotary evaporator, the residue is purified by fractional distillation using a Vigreux colum.

B. (-)-(S)-2-(Benzyloxy)propanal . A flame-dried, 500-mL Schlenk flask equipped with a magnetic stirring bar, dropping funnel sealed with a rubber septum, and an argon balloon is loaded under an atmosphere of argon with 18.7 g (90 mmol) of (-)-(S)-ethyl 2-(benzyloxy)propanoate and the compound is dissolved in anhydrous diethyl ether (180 mL). The reaction mixture is cooled to -78°C by means of a cooling bath (dry ice/ethanol). A 1 M solution of diisobutylaluminum hydride (DIBAH) in hexane (126 mL, 126 mmol) is added very slowly dropwise to the solution of the ester and stirring is continued for at least 1 hr after the complete addition of the DIBAH solution. Upon complete consumption of the ester, the crude reaction mixture is poured directly with vigorous stirring into 360 mL of ice cold 4 N hydrochloric acid. The aqueous phase is extracted with diethyl ether (4 × 180 mL) and the combined organic extracts are washed with 50 mL of aqueous saturated NaCl solution. After drying over MgSO₄, filtration and removal of the solvents under reduced pressure by means of a rotary evaporator, 14.4 g (98%) of the crude aldehyde is obtained.

C. (-)-(E,S)-3-(Benzyloxy)-1-butenyl phenyl sulfone . As described in ref. 4, a flame-dried, 500-mL Schlenk flask (or three-necked flask with a thermometer) equipped with a large magnetic stirring bar, dropping funnel sealed with a rubber septum, and an argon balloon is charged and 36.6 g (125 mmol) of diethyl [(phenylsulfonyl)methyl]phosphonate. The reagents are suspended in 250 mL of anhydrous acetonitrile and 19.1 mL (13.9 g, 138 mmol) of triethylamine is then added. The reaction mixture is stirred at room temperature until it becomes homogeneous and is then cooled to 0°C (an ice-salt bath is used to maintain the internal temperature at 0°C). The dropping funnel is charged with a solution of 20.6 g (125 mmol) of (-)-(S)-2-(benzyloxy)propanal in 50 mL of anhydrous acetonitrile . The aldehyde solution is added dropwise at 0°C with vigorous stirring. After complete addition the reaction mixture is stirred for ca. 12 hr and allowed to warm to room temperature during this period. The reaction is monitored by TLC and is halted by the addition of 0.1 N hydrochloric acid (150 mL) and water (150 mL). The reaction mixture is diluted with diethyl ether (200 mL). After phase separation, the aqueous phase is reextracted with diethyl ether (4 × 200 mL) and the combined organic extracts are washed with aqueous saturated NaCl solution (200 mL). After drying over MgSO₄, filtration, and removal of the solvents under reduced pressure using a rotary evaporator, the crude product is purified by column chromatography using a 15 : 1 (w/w) ratio of silica gel to crude product and 1:2  1:1 (v/v) diethyl ether/light petroleum as eluent to yield 34.2 g (90%) of the pure (E)-isomer as a colorless viscous oil.