Method A: A solution of N-boc amine (1.0 equiv.) in TFA (0.2 M) was prepared. The reaction mixture was stirred for 5 min at room temperature. After this time, TFA was removed under reduced pressure. The crude residue was then dissolved in methanol and evaporated under reduced pressure (five times). This operation was reiterated 3 times using chloroform to get the corresponding salt.