Diisopropylethylamine → tert-butyl 3-(2-(2-((2S,5R)-6-(benzyloxy)-7-oxo-1,6-diaza bicyclo[3.2.1]octane-2-carbonyl)hydrazinyl)-2-oxoethyl)azetidine-1-carboxylate

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Reaction Steps

HATU (19.6 g, 52.2 mmol) and DIPEA (16.6 g, 130.5 mmol) were added to a 0° C. solution of (2S,5R)-6-(benzyloxy)-7-oxo-1,6-diaza-bicyclo[3.2.1]octane-2-carboxylic acid (12.0 g, 43.5 mmol), tert-butyl 3-(2-hydrazinyl-2-oxoethyl)azetidine-1-carboxylate (11.3 g, 49.8 mmol) in CH2Cl2 (360 mL). The mixture was allowed to warm to rt then the mixture was stirred at rt for 12 hrs. The mixture was then diluted with CH2Cl2 (300 mL), washed with water (2×) and saturated sodium chloride (2×), dried and concentrated. The residue was purified by silica gel column chromatography (0-20% gradient elution EtOAc/petroleum ether) to afford tert-butyl 3-(2-(2-((2S,5R)-6-(benzyloxy)-7-oxo-1,6-diaza bicyclo[3.2.1]octane-2-carbonyl)hydrazinyl)-2-oxoethyl)azetidine-1-carboxylate (19.3 g, 93%) as a white solid. ESI-MS (EI+, m/z): 488 [M+H]+.

Provenance & Evidence