(1R,3R)-3-((tert-Butoxycarbonyl)amino)cyclopentanecarboxylic acid → tert-butyl (1R,3R)-3-(2-(5-tosyl-5H-pyrrolo[2,3-b]pyrazin-2-yl)hydrazinecarbonyl)cyclopentylcarbamate

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Reaction Steps

To (1R,3R)-3-(tert-butoxycarbonylamino)cyclopentanecarboxylic acid (2.25 g, 9.81 mmol, Acros) in DCM (98 mL) was added 2-hydrazinyl-5-tosyl-5H-pyrrolo[2,3-b]pyrazine (2.98 g, 9.81 mmol), HATU (3.73 g, 9.81 mmol) and TEA (5.5 mL, 39 mmol). The reaction mixture was stirred at ambient temperature for about 4 h then diluted with DCM (300 mL). The reaction mixture was washed with water (2×80 mL), saturated aqueous NaHCO3 (80 mL), dried over anhydrous MgSO4, filtered, and concd under reduced pressure. The residue was purified using silica gel chromatography (220 g) eluting with a gradient of 50-100% EtOAc in DCM give tert-butyl (1R,3R)-3-(2-(5-tosyl-5H-pyrrolo[2,3-b]pyrazin-2-yl)hydrazinecarbonyl)cyclopentylcarbamate (5.03 g, 100%) as a brown solid: LC/MS (Table 1, Method b) Rt=2.18 min; MS m/z: 513 (M−H)−

Provenance & Evidence