Studies related to the chemistry of melanins. Part VI. Syntheses of 3-carboxypyrrole-2-acetic acid, 3,5-dicarboxypyrrole-2-acetic acid, and related compounds

The acids named in the title were synthesised. In the case of pyrroles already containing an ester group, a carboxylic function can be introduced by use of phosgene, but better by use of oxalyl chloride; and acetic ester group can be introduced by use of diazoacetic ester. Some pyrroles containing carboxy- or ester groups are N-methylated by diazomethane.