[Chemical structure and anti-inflammatory activity in the group of substituted indole-3-acetic acids (author's...

The chemical structure of the indometacin molecule was systematically modified with the aim of producing a substance with increased anti-inflammatory activity and improved tolerance. In addition to the variations of the methylene group of the indole-3-acetic acid and substituents on the indole nucleus of indometacin, particular attention was paid to the modification of the carboxyl group of the acetic acid side chain. Among the indometacin esters, one derivative, the [1-(4-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetoxy] acetic acid (54), showed an activity approximately twice that of indometacin in the kaolin edema test in the rat paw. Chemical modification of the new compound 54 did not further improve the activity. These studies suggest that specific substitutions on the indole nucleus, in combination with the acetic acid side chain as in 1, and especially the acetoxy acetic acid side chain in 54 are responsible for the high anti-inflammatory activity of this class of substances. Several methods for the synthesis of acemetacin are described.