After 1-methyl-4-nitropyrrole-2-carboxylic acid methyl ester (1.17 g, 6.35 mmol) was dissolved in EA (20 ml), 10% Pd/C (50 mg, catalytic weight) was added thereto. The mixture was stirred for 1 hour at room temperature under hydrogen atmosphere to reduce a nitro group (NO2) into an amino group (NH2), whereby a pyrrole-type amino acid was obtained. 10% Pd/C was filtered out by celite 545 filter, and the filtrate was washed with EA and MeOH and concentrated under vacuum. To the residue were added carbonic acid 4-nitro-phenyl ester 2-(4-trifluoromethyl-phenylsulfanyl)-ethyl ester (2.23 g, 5.76 mmol) dissolved in anhydrous DCM (30 ml), DIEA (2.01 μm, 11.56 mmol), DMAP (1.41 g, 11.56 mmol), and HOBt (1.77 g, 11.56 mmol), and the mixture was stirred for 12 hours at room temperature. The reaction was stopped by adding water and the reaction mixture was extracted with DCM. The organic layer was dried over anhydrous MgSO4 and concentrated. The residue was purified by silica gel column chromatography (EA/n-hexane=1/3, v/v) to give methyl 1-methyl-4-[2-(4-trifluoromethyl-phenylsulfanyl)-ethoxycarbonylamino]-1H-pyrrole-2-carboxylate (1.98 g, 85.42%) of a pale yellow solid.
