Hexane → Methyl 3-{[butyl(methyl)amino]methyl}-5-(1,3-oxazol-2-yl)benzoate

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To an ice-cold solution of 3-(methoxycarbonyl)-5-(1,3-oxazol-2-yl)benzoic acid (340 mg, 1.4 mmol) in anhydrous tetrahydrofuran (10 mL) is added lithium borohydride (250 mg, 11 mmol) slowly. The reaction is stirred 30 min, then absolute ethanol (4 mL) is added, and the reaction is stirred 1 h. The solution is poured onto ice containing excess hydrochloric acid and extracted with ethyl acetate. The organic layer is washed with water, brine, dried (sodium sulfate), filtered, and concentrated under reduced pressure. The residue is redissolved in 20% methanol/benzene (50 mL), and 2M trimethylsilyldiazomethane in hexane (0.9 mL, 1.8 mmol) is added. The reaction is stirred 2 h at room temperature, then concentrated under reduced pressure. The residue is redissolved in anhydrous methylene chloride (10 mL), cooled to −30° C., then methanesulfonyl chloride (150 μL, 1.9 mmol) and triethylamine (380 μL, 2.7 mmol) are added. The reaction is stirred at 0° C. 15 min, then N-methylbutylamine (480 μL, 4 mmol) is added, and the reaction is stirred 16 h at room temperature. The solution is concentrated under reduced pressure. Purification by flash column chromatography (silica gel, 40-100% ethyl acetate/hexane gradient) provides the title compound in pure form. ESI MS m/z 303.3 [M+H]+.

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