The quinoline alkaloids are derived from anthranilic acid. More than 80 new quinoline alkaloids have been isolated, a new group, the dimeric quinolinones, has been discovered, and considerable advances have been made in the synthesis of the alkaloids. Spectroscopic methods continue to be crucial in the elucidation of the structures of quinoline alkaloids. This chapter reviews various quinoline alkaloids, their structure, preparation and biosynthesis. Derivatives of 4-hydroxy-2-quinolinone are discussed along with 3-prenyl-2-quinolinones, derived by C-allylation of intermediate 4-hydroxy-2-quinolinone. The 3-prenyl-2-quinolinones occupy a central position in the sequence; oxidative cyclization leads to dihydropyranoquinolines or dihydrofuroquinolines exemplified by isobalfourodine and platydesmine, respectively; dehydration of the latter compounds may be responsible for example, for the formation of terminal olefins. On the other hand, oxidation of 3-prenyl-2-quinolinones to a diene 4 provides the opportunity for intramolecular cyclization to the large group of dimethylpyranoquinolinones, and intermolecular addition to give dimeric quinolinone alkaloids. © 1988 Academic Press, Inc.