Alkaloids Derived from Anthranilic Acid

Derived from Ornithine
  - Pyrrolidine & Tropane
  - Pyrrolizidine
Derived from Lysine
  - Piperidine
  - Quinolizidine
  - Indolizidine
Derived from Nicotinic Acid
  - Pyridine
Derived from Tyrosine
  - PEA & Simple TIQ
  - Modified BTIQ
  - Phenethylisoquinoline
  - Terpenoid TIQ
  - Amaryllidaceae
Derived from Tryptophan
  - Simple Indole
  - Simple β-Carboline
  - Terpenoid Indole
  - Quinoline
  - Pyrroloindole
  - Ergot
Derived from Anthranilic Acid
  - Quinazoline
  - Quinoline & Acridine
Derived from Histidine
  - Imidazole
Derived by Amination Reactions
  - Acetate-derived
  - Phenylalanine-derived
  - Terpenoid
  - Steroidal
Purine Alkaloids
  - Saxitoxin & Tetrodotoxin

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.

Figure 106