Methanol → 3-methyl-5-[3-(2-pyrrolidin-1-yl-ethylamino)-propyl]-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester

5-(3-Methanesulfonyloxy-propyl)-3-methyl-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester 1 g (8.462 g, 21.75 mmol) was dissolved in 2-pyrrolidin-1-yl-ethylamine (6.3 ml, 49.79) under stirring, the resulting solution was stirred at room temperature overnight. After thin lay chromatography showed the disappearance of starting materials, the reaction mixture was added with ethyl acetate (200 ml) and a little methanol until a clear solution was obtained. The mixture was washed with water (30 ml×3), saturated brine (40 ml×2) and concentrated under reduced pressure to obtain light brown oil. The oil was purified by silica gel column chromatography to obtain the title compound 3-methyl-5-[3-(2-pyrrolidin-1-yl-ethylamino)-propyl]-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester 28a (4.488 g, yield 63.5%) as a yellow oil.