[C:1]([O:5][C:6]([N:8]1[C@@H:13]([CH2:14][OH:15])[CH2:12][O:11][C@@H:10]([CH2:16][CH2:17][CH:18]2[CH2:23][CH2:22][CH2:21][CH2:20][CH2:19]2)[CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].C(N(CC)CC)C.O>CS(C)=O.C(OCC)(=O)C>[C:1]([O:5][C:6]([N:8]1[C@@H:13]([CH:14]=[O:15])[CH2:12][O:11][C@@H:10]([CH2:16][CH2:17][CH:18]2[CH2:19][CH2:20][CH2:21][CH2:22][CH2:23]2)[CH2:9]1)=[O:7])([CH3:4])([CH3:2])[CH3:3]Dissolve 2-(S)-(2-cyclohexylethyl)-5-(S)-hydroxymethylmorpholine-4-carboxylic acid tert-butyl ester (165 mg, 0.50 mmol) in dimethylsulfoxide (2 mL), and cool to 10° C. Add triethylamine (0.28 mL, 2.02 mmol) followed by pyridine sulfur trioxide complex and stir for 30 min. Dilute with ethyl acetate and pour into cold water. Wash with 5% citric acid (50 mL), saturated aqueous sodium chloride (50 mL) and dry (sodium sulfate), filter and concentrate give the desired compound as an oil which is used without further purification.
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