(6-Chloro-1H-benzotriazol-1-yloxy)tripyrrolidinophosphonium Hexafluorophosphate

Experimental procedure:
1 (0.5 g, 2.75 mmol) is dissolved in CH₂Cl₂ (5 mL). 2 (2.2 g, 5.5 mmol), DIEA (1.9 mL, 1.1 mmol), and TPTDP (3.057 g, 5.5 mmol) are dissolved in CH₂Cl₂ (5 mL). After 2 is dissolved, it is added to the solution of 1 and stirred overnight. The mixture is concentrated under reduced pressure. The methyl ester is removed using 1 mol/L LiOH (30 mL)/MeOH (70 mL) for 4 h. The mixture is acidified by the addition of 3 mol/L HCl (30 mL). MeOH is then removed by evaporation. Ethyl acetate (50 mL) and saturated NaCl (100 mL) is added, followed by extraction 4 times with ethyl acetate (50mL). The organic fractions are combined and the ethyl acetate is concentrated under reduced pressure. The crude is purified by RP-HPLC (CH₃CN:H₂O:TFA) to give 3 as a white solid.