A solution of 2-[4-(methylsulfonylamino)phenyl]-2-methylpropionic acid (8-11, 1 mmol) in toluene (6 mL) was treated with 4A molecular sieve (200 mg), Et3N (1.3 mmol) and diphenylphosphoryl azide (1.3 mmol) and heated at 110° C. for 1 h. The mixture was cooled to room temperature and BnOH (20 mmol) was added. After the mixture was heated to 110° C. for 12 hours and concentrated in vacuo. The residue was purified by column chromatography on silica gel with EtOAc:hexanes as eluant to afford Benzyl N-{1-Methyl-1-[4-(methylsulfonylamino)phenyl]ethyl}carbamate (21-1, CHK-582)
