To a solution of 4-[[[4-(2-Butynyloxy)phenyl]sulfonyl]methyl]-4-piperidinecarboxylic acid ethyl ester (0.354 g, 0.85 mmol) in 1.0 mL of CH2Cl2 under N2 atmosphere was added dropwise a solution of N,O-bis(trimethylsilyl)acetamide (0.462 ml, 1.87 mmol) in 0.5 mL of CH2Cl2 and stirred for 1 h. The reaction was cooled to 0° C. and added dropwise a solution of 0.079 mL (1.02 mmol) of methylchloroformate in 0.5 mL of CH2Cl2. The reaction was allowed to stir at room temperature for 1 h and cooled to 0° C., quenched with pH 7 buffer solution and extracted with EtOAc. The organics was washed with H2O, brine, dried over MgSO4, filtered, and concentrated in vacuo. The residue was chromatographed on silica gel eluting with EtOAc:hexanes (1:2) to provide 0.315 g (85%) of the desired product as a colorless oil. Electrospray Mass Spec: 438.3 (M+H)+
