To a solution of 2-(tert-butoxycarbonylamino)-2-(4-fluorophenyl)acetic acid (I49) (725 mg, 2.69 mmol) in THF (20 ml), were added N,N′-methanediylidenedicyclohexanamine (667 mg, 3.23 mmol), 1H-benzo[d][1,2,3]triazol-1-ol (437 mg, 3.23 mmol), and (R)-quinuclidin-3-ol (411 mg, 3.23 mmol). The reaction was stirred at RT for 15 hours, and the solvent was evaporated. The residue was taken up with DCM, the insoluble solid was filtered off, and the organic solution was washed twice with aq. Na2CO3 and then brine, dried over Na2SO4 and evaporated. The crude was purified by flash chromatography (DCM/MeOH=95/5 to 93/7) to obtain (R)-quinuclidin-3-yl 2-(tert-butoxycarbonylamino)-2-(4-fluorophenyl)acetate (410 mg; 40% yield).
