Alkaloids Derived from Anthranilic Acid

Anthranilic acid (Figure 106) is a key intermediate in the biosynthesis of L-tryptophan and so contributes to the elaboration of indole alkaloids. During this conversion, the anthranilic acid residue is decarboxylated, so that only the C₆N skeleton is utilized. However, there are also many examples of where anthranilic acid itself functions as an alkaloid precursor, using processes which retain the full skeleton and exploit the carboxyl (Figure 106). It should also be appreciated that, in mammals, L-tryptophan can be degraded back to anthranilic acid , but this is not a route of importance in plants.