Triphenylphosphine → 5-bromo-3-[2(R)-tert-butoxycarbonylamino-2-cyclohexylethyl]-1-[2,6-difluorobenzyl]-6-methyl-pyrimidine-2,4(1H,3H)-dione

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Reaction Steps

A solution of tert-butyl 1-cyclohexyl-2-hydroxyethylcarbamate 4a (638 mg, 2.62 mmol) in THF (10 mL) was treated with 5-bromo-1-(2,6-difluorobenzyl)-6-methylpyrimidine-2,4(1H,3H)-dione 1d.1 (869 mg, 2.62 mmol) and triphenylphosphine (1.03 g, 3.93 mmol) at ambient temperature, then di-tert-butylazodicarboxylate (906 mg, 3.93 mmol) was introduced. The reaction mixture was stirred at ambient temperature for 16 hours and volatiles were evaporated. The residue was partitioned between saturated NaHCO3/H2O and EtOAc. The organic layer was dried (sodium sulfate), evaporated, and purified by flash chromatography (silica, 25% EtOAc/hexanes) to give compound 4b (1.39 g, 95.4% ). MS (CI) m/z 456.1, 458.1 (MH+-Boc).

Provenance & Evidence