Benzyl chloroformate → Tert-butyl 6-benzyloxycarbonylamino-3-bromo-2-(4-methylbenzenesulfonyloxy)benzoate

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Reaction Steps

Benzyl chloroformate (1.705 g) was added to a stirred solution of tert-butyl 6-amino-3-bromo-2-(4-methylbenzensulfonyloxy)-benzoate (Intermediate 50, 3.8 g) in pyridine (50 mL) with cooling in ice. The mixture was stirred for 1 hour and further benzyl chloroformate (1.70 g) was added. The mixture was stirred for a further 1 hour and further benzyl chloroformate (1.70 g) was added. After stirring for a further 30 minutes, the solution was concentrated in vacuo and the residue was dissolved in DCM and 1M hydrochloric acid and filtered through a phase separator. The filtrate was concentrated in vacuo and the residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane with a gradient of 0-15% to give tert-butyl 6-benzyloxycarbonylamino-3-bromo-2-(4-methylbenzenesulfonyloxyl)benzoate (4.91 g) as a white solid.

Provenance & Evidence