Shoji, Yujiro Hayashi*

Typical procedure for a synthesis of (2S, 4R)-4-decanoyloxypyrrolidine-2-carboxylic acid (2S, 4R)-N-Benzyloxycarbonyl-4-decanoyloxypyrrolidine-2-carboxylic acid benzyl ester (9c) To a solution of (2S, 4R)-N-benzyloxycarbonyl-4-hydroxypyrrolidine-2-carboxylic acid benzyl ester 8 (2.34 g, 4.50 mmol) and catalytic amount of 4-dimethylaminopyridine in pyridine (9.0 mL) was added n-decanoyl chloride (1.37 mL, 6.75 mmol) successively at 0 °C. After stirring the reaction mixture for 18h at that temperature to room temperature, the reaction was quenched with saturated NaHCO3 aqueous solution and the organic materials were extracted with ethyl acetate three times. The combined organic extracts were washed with saturated NaHCO3 aqueous solution and brine each three times, dried over anhydrous Na2SO4, and concentrated in vacuo after filtration. Purification by silica gel chromatography (ethyl acetate: hexane = 1: 12) gave (2S, 4R)-N-benzyloxycarbonyl-4-decanoyloxypyrrolidine-2-carboxylic acid benzyl ester 9c (2.06 g, 3.96 mmol) in 88 % yield as a colorless oil