The condensation of dimethylacetone-1,3-dicarboxylate (X) with ethanolamine (XI) yields methyl 3-(methoxycarbonylmethyl)-3-(2-hydroxyethylamino)acrylate (XII), which is cyclized with bromoacetaldehyde diethylacetal (XIII) affording methyl 1-(2-hydroxyethyl)-3-methoxycarbonylpyrrol-2-acetate (XIV). Acylation of (XIV) with methanesulfonyl chloride (XV) and triethylamine in CH2Cl2 yields the corresponding mesylate (XVI), which by treatment with methyl iodide in refluxing acetonitrile is converted into methyl 1-(2-iodoethyl)-3-methoxycarbonylpyrrole-2-acetate (XVII). The cyclization of (XVII) with NaH in DMF yields dimethyl 1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1,7-dicarboxylate (XVIII), which is hydrolyzed with KOH in refluxing methanol - water to the corresponding diacid (XIX). Partial esterification of (XIX) with isopropanol and HCl gives isopropyl 1,2-dihydro-3H-7-carboxypyrrolo[1,2-a]pyrrole-1-carboxylate (XX), which is decarboxylated by heating at 270 C affording isopropyl 1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylate (XXI). Benzoylation of (XXI) with N,N-dimethylbenzamide (XXII) and POCl3 in refluxing CH2Cl2 yields isopropyl 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylate (XXIII), which is finally hydrolyzed with K2CO3 or NaOH in methanol - water.

The benzoylation of 2-methylthiopyrrole (I) with N,N-dimethylbenzamide (II) by means of POCl3 in refluxing CH2Cl2 gives 5-benzoyl-2-methylthiopyrrole (III), which is condensed with spiro[2.5]-5,7-dioxa-6,6-dimethyloctane-4,8-dione (IV) by means of NaH in DMF yielding compound (V). The oxidation of (V) with m-chloroperbenzoic acid in CH2Cl2 affords the sulfone (VI), which is submitted to methanolysis with methanol and HCl giving 1-(3,3-dimethoxycarbonylpropyl)-2-methanesulfonyl-5-benzoylpyrrole (VII). The cyclization of (VII) with NaH in DMF yields dimethyl 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1,1-dicarboxylate (VIII), which is finally hydrolyzed and decarboxylated with KOH in refluxing methanol. Compound (III) can be oxidized with m-chloroperbenzoic acid as before giving 2-methanesulfonyl-5-benzoylpyrrole (IX), which is then condensed with spiro compound (IV) as before to afford compound (VI), already obtained.

The condensation of dimethylacetone-1,3-dicarboxylate (X) with ethanolamine (XI) yields methyl 3-(methoxycarbonylmethyl)-3-(2-hydroxyethylamino)acrylate (XII), which is cyclized with bromoacetaldehyde diethylacetal (XIII) affording methyl 1-(2-hydroxyethyl)-3-methoxycarbonylpyrrol-2-acetate (XIV). Acylation of (XIV) with methanesulfonyl chloride (XV) and triethylamine in CH2Cl2 yields the corresponding mesylate (XVI), which by treatment with methyl iodide in refluxing acetonitrile is converted into methyl 1-(2-iodoethyl)-3-methoxycarbonylpyrrole-2-acetate (XVII). The cyclization of (XVII) with NaH in DMF yields dimethyl 1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1,7-dicarboxylate (XVIII), which is hydrolyzed with KOH in refluxing methanol - water to the corresponding diacid (XIX). Partial esterification of (XIX) with isopropanol and HCl gives isopropyl 1,2-dihydro-3H-7-carboxypyrrolo[1,2-a]pyrrole-1-carboxylate (XX), which is decarboxylated by heating at 270 C affording isopropyl 1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylate (XXI). Benzoylation of (XXI) with N,N-dimethylbenzamide (XXII) and POCl3 in refluxing CH2Cl2 yields isopropyl 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylate (XXIII), which is finally hydrolyzed with K2CO3 or NaOH in methanol - water.

The condensation of dimethylacetone-1,3-dicarboxylate (X) with ethanolamine (XI) yields methyl 3-(methoxycarbonylmethyl)-3-(2-hydroxyethylamino)acrylate (XII), which is cyclized with bromoacetaldehyde diethylacetal (XIII) affording methyl 1-(2-hydroxyethyl)-3-methoxycarbonylpyrrol-2-acetate (XIV). Acylation of (XIV) with methanesulfonyl chloride (XV) and triethylamine in CH2Cl2 yields the corresponding mesylate (XVI), which by treatment with methyl iodide in refluxing acetonitrile is converted into methyl 1-(2-iodoethyl)-3-methoxycarbonylpyrrole-2-acetate (XVII). The cyclization of (XVII) with NaH in DMF yields dimethyl 1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1,7-dicarboxylate (XVIII), which is hydrolyzed with KOH in refluxing methanol - water to the corresponding diacid (XIX). Partial esterification of (XIX) with isopropanol and HCl gives isopropyl 1,2-dihydro-3H-7-carboxypyrrolo[1,2-a]pyrrole-1-carboxylate (XX), which is decarboxylated by heating at 270 C affording isopropyl 1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylate (XXI). Benzoylation of (XXI) with N,N-dimethylbenzamide (XXII) and POCl3 in refluxing CH2Cl2 yields isopropyl 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1-carboxylate (XXIII), which is finally hydrolyzed with K2CO3 or NaOH in methanol - water.

The benzoylation of 2-methylthiopyrrole (I) with N,N-dimethylbenzamide (II) by means of POCl3 in refluxing CH2Cl2 gives 5-benzoyl-2-methylthiopyrrole (III), which is condensed with spiro[2.5]-5,7-dioxa-6,6-dimethyloctane-4,8-dione (IV) by means of NaH in DMF yielding compound (V). The oxidation of (V) with m-chloroperbenzoic acid in CH2Cl2 affords the sulfone (VI), which is submitted to methanolysis with methanol and HCl giving 1-(3,3-dimethoxycarbonylpropyl)-2-methanesulfonyl-5-benzoylpyrrole (VII). The cyclization of (VII) with NaH in DMF yields dimethyl 5-benzoyl-1,2-dihydro-3H-pyrrolo[1,2-a]pyrrole-1,1-dicarboxylate (VIII), which is finally hydrolyzed and decarboxylated with KOH in refluxing methanol. Compound (III) can be oxidized with m-chloroperbenzoic acid as before giving 2-methanesulfonyl-5-benzoylpyrrole (IX), which is then condensed with spiro compound (IV) as before to afford compound (VI), already obtained.