Trifluoroacetic acid → Methanol trifluoroacetic acid

A solution of lithium aluminum hydride (1.0 M, 0.24 mL, 0.24 mmol) was added at 0° C. to a solution of 4-[benzo[b]thiophen-5-yl-(3-carboxy-benzyl)-amino]-piperidine-1-carboxylic acid tert-butyl ester (55 mg, 0.12 mmol) in THF (2 mL). The reaction mixture was stirred for 1 hour and it was then quenched by addition of water, MeOH (1 drop) and an aqueous solution of KOH (15%, 2 drops). The resulting mixture was stirred for 15 minutes and it was filtered over a celite pad. The filtrate was evaporated under reduced pressure and the crude residue was purified by preparative TLC (6/4, hexane/EtOAc) to give 20 mg of 4-[benzo[b]thiophen-5-yl-(3-hydroxymethyl-benzyl)-amino]-piperidine-1-carboxylic acid tert-butyl ester as a colorless oil. This material was dissolved in DCM (2 mL) and trifluoroacetic acid (100 μL) was added, the resulting mixture was stirred overnight. The solvent was evaporated under reduced pressure and the residue was triturated with Et2O to give 3 mg of 3-{[(1H-indol-5-yl)-piperidin-4-yl-amino]-methyl}-phenyl)-methanol trifluoroacetate as a gray powder.