[C:1]([C:6]1[NH:7][C:8]([CH2:12][CH3:13])=[C:9]([CH3:11])[CH:10]=1)([O:3][CH2:4][CH3:5])=[O:2].[CH:14](=O)[CH:15]([CH3:17])[CH3:16]>>[C:1]([C:6]1[NH:7][C:8]([CH2:12][CH3:13])=[C:9]([CH3:11])[C:10]=1[CH2:14][CH:15]([CH3:17])[CH3:16])([O:3][CH2:4][CH3:5])=[O:2]The crude product, obtained in Example 68 but using 2-carbethoxy-4-methyl-5-ethylpyrrole and isobutyraldehyde, solidified at 0° C. after distillation (70° C. 1 × 10-4 mm). It was recrystallized twice from methanol, m.p. 53°-55° C. (12%).
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