Diphenylchlorophosphate (96 μL, 124 mg, 0.46 mmol) was added drop-wise to a solution of the benzofuran-2-carboxylic acid (75 mg, 0.46 mmol) and triethylamine (64 μL, 46 mg, 0.46 mmol) in dry dichloromethane (1 mL). After stirring at ambient temperature for 45 min, a solution of (2R,3S)-3-amino-2-((3-pyridinyl)methyl)-1-azabicyclo[2.2.2]octane (0.10 g, 0.46 mmol) (that derived from the di-p-toluoyl-L-tartaric acid salt) and triethylamine (64 μL, 46 mg, 0.46 mmol) in dry dichloromethane (1 mL) was added. The reaction mixture was stirred overnight at ambient temperature, and then treated with 10% sodium hydroxide (1 mL). The biphasic mixture was separated, and the organic layer and a chloroform extract (2 mL) of the aqueous layer was concentrated by rotary evaporation. The residue was dissolved in methanol and purified by HPLC on a C18 silica gel column, using an acetonitrile/water gradient, containing 0.05% trifluoroacetic acid, as eluent. Concentration of selected fractions, partitioning of the resulting residue between chloroform and saturated aqueous sodium bicarbonate, and evaporation of the chloroform gave 82.5 mg (50% yield) of a white powder. The NMR spectrum was identical to that obtained for the 2S,3R isomer.
