Hydrochloric Acid → (E)-4-butyramido-1-methyl-2-pyrroleacrylic acid

A solution of 4 (0.167 g, 0.667 mmol) and 0.2 M aqueous NaOH (5.7 mL, 1.13 mmol) in MeOH (10 mL) was heated under reflux for 50 min. The mixture was cooled to 0° C., 2 M aqueous HCl (0.67 mL, 1.33 mmol) was added, and the mixture was poured onto ice (50 g). The precipitate that formed was collected by filtration and washed with water to give (E)-4-butyramido-1-methyl-2-pyrroleacrylic acid (5) as yellow needles (0.133 g, 85%) mp 74-76° C. (dec.) and 165-166° C. (with evolution of gas). 1H NMR [(CD3)2SO] δ12.02 (br s, 1 H, CO2H), 9.76 (br s, 1 H, CONH), 7.44 (d, J=15.6 Hz, 1 H, H-β), 7.27 (d, J=1.6 Hz, 1 H, H-5), 6.53 (d, J=1.6 Hz, 1 H, H-3), 6.02 (d, J=15.6 Hz, 1 H, H-α), 3.66 (s, 3 H, NCH3), 2.19 (t, J=7.3 Hz, 2 H, CH2CH2CH3), 1.57 (sx, J=7.3 Hz, 2 H, CH2CH2CH3), 0.88 (t, J=7.3 Hz, 3 H, CH2CH2CH3). 13C NMR δ169.2, 168.0 (NHCO, CO2), 131.9, 117.8, 113.6, 101.9 (C-3, 5, α, β), 125.8, 124.2 (C-2, 4), 37.5 (CH2CH2CH3), 33.6 (NCH3), 18.7 (CH2CH2CH3), 13.6 (CH2CH2CH3) Anal. Calculated for C12H16N2O4: C, 61.0; H, 6.8; N, 11.9. Found: C, C, 60.8; H, 8.4; N, 11.7%.