Diisopropylethylamine → (S)-3-methyl-2-{4'-[(4-methyl-benzooxazole-2-carbonyl)-amino]-biphenyl-4-sulfonylamino}-butyric acid tert-butyl ester

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Reaction Steps

To 4-methyl-benzooxazole-2-carboxylic acid sodium salt (180 mg, 0.93 mmol) was added (S)-2-(4′-amino-biphenyl-4-sulfonylamino)-3-methyl-butyric acid tert-butyl ester (450 mg, 1.2 eq), BOP (490 mg, 1.2 eq), N,N-diisopropylethylamine (144 mg, 1.2 eq) and 4 mL of DMF. The mixture was stirred at room temperature overnight. The reaction mixture was poured into brine, and extracted with ethyl acetate. The combined organic solution was washed with brine and water. Removal of the solvent in vacuo gave the crude product, which was purified by column chromatography on silica gel to give 158 mg of (S)-3-methyl-2-{4′-[(4-methyl-benzooxazole-2-carbonyl)-amino]-biphenyl-4-sulfonylamino}-butyric acid tert-butyl ester as a white solid.

Provenance & Evidence