[C:1]([O:5][C:6](=[O:19])[NH:7][C@@H:8]1[CH2:13][CH2:12][C@@H:11]([C:14](=O)[CH:15]=[N+]=[N-])[O:10][CH2:9]1)([CH3:4])([CH3:3])[CH3:2].[C:20](OCC)(=[O:22])C.[O:26]1CCCC1>C(N(CC)CC)C.CO.FC(F)(F)C([O-])=O.[Ag+]>[CH3:20][O:22][C:15](=[O:26])[CH2:14][C@@H:11]1[CH2:12][CH2:13][C@@H:8]([NH:7][C:6]([O:5][C:1]([CH3:2])([CH3:3])[CH3:4])=[O:19])[CH2:9][O:10]1A solution of silver trifluoroacetate (124 mg, 0.56 mmol, 0.4 eq) in triethylamine (0.5 mL) is added at 0° C. to a stirred solution of (3R,6S)-[6-(2-diazo-acetyl)-tetrahydro-pyran-3-yl]-carbamic acid tert-butyl ester (380 mg, 1.41 mmol, 1.0 eq) in tetrahydrofuran (20 mL) and methanol (20 mL). After 1 hour stirring at room temperature, solvents are removed and the crude product is purified by column chromatography (silica gel, eluent: petroleum ether:ethyl acetate, 10:1 to 3:1, v/v) to afford (2S,5R)-(5-tert-butoxycarbonylamino-tetrahydro-pyran-2-yl)-acetic acid methyl ester as a white solid (200 mg, 52% yield).
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