Methyl 4-aminobenzoate → Methyl 4-{[1-(5-methoxy-3-methyl-1-benzofuran-2-yl)-5-(methylsulfanyl)pentyl]amino}benzoate

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Reaction Steps

To a mixture of 1-(5-methoxy-3-methyl-1-benzofuran-2-yl)-5-(methylsulfanyl)pentan-1-one (658 mg) synthesized above, methyl 4-aminobenzoate (375 mg), triethylamine (2.50 mL) and methylene chloride (10 mL) was added a 1.0M solution (2.70 mL) of titanium (IV) chloride in methylene chloride at 0° C., and the mixture was stirred under argon atmosphere at room temperature for 3.5 days. Saturated aqueous sodium hydrogen carbonate solution was added to quench the reaction, methylene chloride was evaporated in an evaporator, and the residue was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure to give a dark brown oil. To a solution (10 mL) of the obtained oil in tetrahydrofuran were added acetic acid (647 μL) and sodium cyanoborohydride (283 mg), and the mixture was stirred at room temperature for 1 hr. Saturated aqueous sodium hydrogen carbonate solution was added to quench the reaction, and the reaction mixture was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (0-50% ethyl acetate/hexane) to give the so title object compound (645 mg, 67%) as a brown oil.

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