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The 5-(4-chlorobenzoyl)-2-chloro-1-[2-(2,2-dimethyl-4,6-dioxo-1,3-dioxan-5-yl)ethyl]pyrrole sodium salt from Example 3A was dissolved in methanol saturated with hydrogen chloride (30 mL) and stirred at 0° C. for three hours. The solution was diluted with methanol (30 mL) and allowed to warm to room temperature, and was then stirred for another four hours. The solvent was then evaporated under reduced pressure at 10°-20° C. The residue was partitioned between ether and water (150 mL+50 mL), and the water was extracted with ether (2×150 mL). The combined ether extracts were dried over anhydrous sodium sulfate and evaporated to dryness. The residue was chromatographed on Florisil® (50 g/g mixture), eluting the product with hexane/ethyl acetate, 7:3. The product so obtained (1.912 g, 68%) was a colorless crystalline solid, which was recrystallized from dichloromethane/hexane to afford 5-(4-chlorobenzoyl)-2-chloro-1-[3,3-di(methoxycarbonyl)propyl]pyrrole, having the following properties:

1. temperatureto warm to room temperature
2. stirringwas then stirred for another four hours
3. customThe solvent was then evaporated under reduced pressure at 10°-20° C
4. customThe residue was partitioned between ether and water (150 mL+50 mL)
5. extractionthe water was extracted with ether (2×150 mL)
6. dry with materialThe combined ether extracts were dried over anhydrous sodium sulfate
7. customevaporated to dryness
8. customThe residue was chromatographed on Florisil® (50 g/g mixture)
9. washeluting the product with hexane/ethyl acetate, 7:3
10. customThe product so obtained (1.912 g, 68%)
11. customwas recrystallized from dichloromethane/hexane