Erythrol-1-(3-Hydroxy-2-methyl-3-phenylpropanoyl)piperidine could be produced through the following synthetic routes.

A. 1-(2-Benzoylpropanoyl)piperidine (CAS NO.: 99114-34-8). A dry, 300-mL, two-necked, round-bottomed flask is equipped with a magnetic stirrer and charged with nitrogen. One neck is connected to a three-way stopcock equipped with a balloon filled with nitrogen, and the other neck is capped with a rubber septum. The flask is charged with 100 mL of anhydrous tetrahydrofuran (THE) and 10.1 g (14.1 mL, 0.100 mol) of diisopropylamine and immersed in an acetone–dry ice bath. A 1.68 M hexane solution of butyllithium (60 mL, 0.10 mol) is added dropwise with stirring over a 10-min period, and the stirring is continued for 1 hr at -78°C. To the resulting lithium diisopropylamide (LDA) solution is added dropwise 14.1 g (0.100 mol) of propanoylpiperidine with stirring over a 10-min period, and the stirring is continued for 2 hr at -78°C. The rubber septum is replaced with a polyvinyl chloride (or ) tube connected to another 300-mL, two-necked, round-bottomed flask, which is equipped with a magnetic stirrer and a three-way stopcock, charged with 100 mL of anhydrous THF and 13.5 g (16.3 mL, 0.110 mol) of benzoyl chloride, and immersed in an acetone–dry ice bath. The balloon is taken off and nitrogen is passed through the two stopcocks so that the reaction mixture does not come in contact with air (see the apparatus shown in Fig. 1). By inclining the first flask, the THF solution of the lithium enolate of 1-propanoylpiperidine is added to the THF solution of benzoyl chloride in the second flask through the polyvinyl chloride tube over a 5-min period. After the solution is stirred for 0.5 hr at -78°C, it is allowed to warm to room temperature, diluted with 200 mL of dichloromethane, and washed with 200 mL of water. The organic layer is separated, and the aqueous layer is extracted with two 50-mL portions of diethyl ether. The combined organic layers are dried over anhydrous magnesium sulfate and concentrated with a rotary evaporator. Recrystallization from diethyl ether–hexane affords 12.5 g (51%) of 1-(2-benzoylpropanoyl)piperidine, mp 100–101°C.

B. erythrol-1-(3-Hydroxy-2-methyl-3-phenylpropanoyl)piperidine. A 300-mL, two-necked, round-bottomed flask is equipped with a magnetic stirrer and charged with nitrogen. One neck is connected with a balloon charged with nitrogen, and the other neck is capped with a rubber septum. Into the flask are placed 50 mL of trifluoroacetic acid and 11.9 g of 1-(2-benzoylpropanoyl)piperidine (48.7 mmol) prepared as described in Part A; then the flask is immersed in an ice–water bath. To the flask is added 7.3 g of dimethylphenylsilane (8.24 mL, 54 mmol) over a 5-min period with the aid of a 10-mL syringe, and the resulting mixture is stirred for 4 hr in the ice bath. The mixture is diluted with 200 mL of dichloromethane and washed with 200 mL of water. After the organic layer is separated, the aqueous layer is extracted with two 50-mL portions of diethyl ether, and the combined organic layers are concentrated with a rotary evaporator. The crude oil is placed in a 200-mL, one-necked flask and dissolved in 100 mL of methanolic 1 M sodium hydroxide. The solution is stirred for 1.5 hr at ambient temperature with a magnetic stirrer. The mixture is diluted with 200 mL of dichloromethane and washed with 50 mL of water. The organic layer is separated, and the aqueous layer is extracted with two 50-mL portions of diethyl ether. The combined organic layers are dried over anhydrous magnesium sulfate and concentrated by rotary evaporation. The residual oil is subjected to column chromatography using 100 g of silica gel. After the first fraction (800t mL) of hexane is eluted, the second fraction, eluted with 500 mL of diethyl ether, is collected and concentrated. Recrystallization of the resulting oil from diethyl ether–hexane gives 10.2 g of material, mp 85–86°C. The yield is 90%.

The analogous threo derivatives can be made by use of tris(diethylamino)sulfonium difluorotrimethylsilicate as the catalyst.