(2S,5R)-6-(Benzyloxy)-7-oxo-1,6-diazabicyclo[3.2.1]octane-2-carboxylic acid → (2S,5R)-methyl 6-(benzyloxy)-7-oxo-1,6-diazabicyclo[3.2.1]octane-2-carboxylate

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Reaction Steps

66 mg (0.239 mmol) of (2S,5R)-6-(benzyloxy)-7-oxo-1,6-diazabicyclo[3.2.1]octane-2-carboxylic acid was dissolved in toluene (0.6 mL) and methanol (0.6 mL), and, under ice cooling, 0.54 mL (0.324 mmol) of 0.6 M trimethylsilyldiazomethane-hexane solution was added, followed by stirring for 20 minutes. The reaction solution was concentrated under reduced pressure, and the resulting residue was subjected to silica gel column chromatography (hexane/ethyl acetate=2/1) to afford 21.5 mg of the title compound as a colorless solid (yield 31%). The resulting solid was recrystallized with ethyl acetate-hexane, the generated precipitate was filtered off, the wet crystal was washed with hexane, and subsequently dried under reduced pressure at room temperature to afford the title compound as a colorless crystalline powder. Enantiomeric excess: 99.9% ee or more (CHIRALPAK AD-H, 4.6×1.50 mm, hexane/ethanol-2/1. UV 210 nm, flow rate 1 mL/min., retention time 12.8 min.). Mp 86° C.; [α]20D+5.3° (c 1.10, CHCl3) 1H NMR (400 MHz, CDCl3, δ): 1.65-1.70 (m, 1H), 2.03-2.12 (m, 3H), 2.90 (d, J=12.0 Hz, 1H), 3.07 (m, 1H), 3.79 (s, 3H), 4.12 (dd, J=4.6, 4.4 Hz, 1H), 4.91 (d, J=11.2 Hz, 1H), 5.06 (d, J=11.2 Hz, 1H), 7.35-7.44 (m, 5H); MS m/z: 291 (M+1).

Provenance & Evidence