Pyridine → (S)-2-{4'-[(4-ethoxy-3-methyl-benzofuran-2-carbonyl)-amino]-biphenyl-4-sulfonylamino}-3-methyl-butyric acid methyl ester

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Reaction Steps

A solution of 115 mg (0.46 mmol) of 4-ethoxy-3-methyl-benzofuran-2-carboxylic acid in 2 mL of oxalyl chloride was refluxed for 4 h in the presence of a catalytic amount of DMF, then the excess oxalyl chloride was removed under vacuum. The residue was dissolved in 2 mL of dichloromethane and was added to a mixture of 201 mg (0.56 mmol) of (S)-2-(4′-amino-biphenyl-4-sulfonylamino)-3-methyl-butyric acid methyl ester, and 2 mL of pyridine in an ice/water bath. The mixture was stirred at room temperature overnight. All the solvents were then removed under vacuum. Column chromatography with silica gel gave 237 mg (93% yield) of (S)-2-{4′-[(4-ethoxy-3-methyl-benzofuran-2-carbonyl)-amino]-biphenyl-4-sulfonylamino}-3-methyl-butyric acid methyl ester as an off white solid.

Provenance & Evidence