[CH3:1][N:2]1[CH:6]=[CH:5][CH:4]=[C:3]1[C:7]([C:9]1[N:13]2[CH2:14][CH2:15][CH:16]([C:17]([O:19]C(C)C)=[O:18])[C:12]2=[CH:11][C:10]=1[CH3:23])=[O:8].CO.C(=O)([O-])[O-].[K+].[K+]>O>[CH3:1][N:2]1[CH:6]=[CH:5][CH:4]=[C:3]1[C:7]([C:9]1[N:13]2[CH2:14][CH2:15][CH:16]([C:17]([OH:19])=[O:18])[C:12]2=[CH:11][C:10]=1[CH3:23])=[O:8]A solution of 500 mg. of isopropyl 5-(N-methyl-2-pyrroyl)-1,2-dihydro-6-methyl-3H-pyrrolo[1,2-a]-pyrrole-1-carboxylate in 15 ml. of methanol is treated with a solution of 1.05 g. of potassium carbonate in 8 ml. of water. The reaction mixture is refluxed under nitrogen atmosphere for 30 minutes, cooled, and evaporated to dryness. The residue is taken up in 10 ml. of 10% aqueous hydrochloric acid and 50 ml. of water and the resultant mixture extracted with ethyl acetate (3 × 50 ml.). The combined extracts are dried over magnesium sulfate and evaporated to dryness under reduced pressure, to give 5-(N-methyl-2-pyrroyl)-1,2-dihydro-6-methyl-3H-pyrrolo[1,2-a]pyrrole-1-carboxylic acid [(A), R and R1 = CH3 ].
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