Formaldehyde → tert-Butyl 3-[{6-[(2-{4-[(biphenyl-2-ylcarbamoyl)oxy]piperidin-1-yl}ethyl)(methyl)amino]-6-oxohexyl}(methyl)amino]benzoate

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Reaction Steps

Moisture was removed from a mixture of the compound (120 mg, 0.205 mmol) obtained in Example 43a and a 35% aqueous formaldehyde solution (85 μL, 1.02 mmol) azeotropically with toluene 3 times. The resulting mixture was dissolved in ethanol (6 mL), sodium triacetoxyborohydride (65 mg, 0.307 mmol) was added under ice cooling, and the mixture was stirred at room temperature under a nitrogen atmosphere for 16 hours. After the reaction was completed, a saturated aqueous sodium hydrogencarbonate solution was added, and ethyl acetate was further added to separate the layers. The resulting organic layer was separated, washed with saturated sodium chloride solution, and then dried with anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by NH silica gel column chromatography (ethyl acetate:methanol, 10:1, v/v) to give the title compound (118 mg; yield, 96%) as a colorless oily substance.

Provenance & Evidence