Trifluoroacetic acid methylene chloride → Trifluoroacetic acid

Tert-butyl (2R,5S)-5-(benzylcarbamoyl)-2-[2-(2-{[N-(methoxycarbonyl)-β-phenyl-L-phenylalanyl]amino}phenyl)ethyl]morpholine-4-carboxylate in a 1:1 mixture of CH2Cl2/TFA (0.1 M) was stirred at rt for 1 hr. The reaction mixture was concentrated under reduced pressure and the residue was co-evaporated twice with heptane and triturated in Et2O to afford the desired product as a TFA salt. Alternatively, the TFA salt, after concentration, could be neutralized with aqueous saturated NaHCO3, extracted with EtOAc, dried over Na2SO4, filtered and concentrated and then purified by automated SiO2 flash chromatography system using solvent gradient of 0% to 10% MeOH/CH2Cl2 to afford the desired compound. Alternatively, the free base could be purified by filtration on SCX SPE cartridge made of pTSA-SiO2 eluted first with MeOH to remove non basic impurities and eluted then with 10% NH4OH/MeOH to elute the free base and afford the desired compound after concentration under reduced pressure.