Heterocyclic Quinones

The quinone moiety is found commonly in nature. Quinones, including heterocyclic analogs, are involved in numerous biochemical processes because of their facile reduction-oxidation. They play an important role in electron transport processes and oxidative phosphorylation processes. Furthermore, their biological activity includes enzyme inhibition and some have chemotherapeutic value as antitumor, antibacterial, antifungal, and anticancer agents. This chapter presents the chemistry of heterocyclic quinones. Only those heterocyclic quinones that have a heterocyclic ring attached directly to the quinone moiety are included. To date, heterocyclic quinones have been partially reviewed, together with naturally occurring quinones, as potential precursors to quinoneimides, together with the quinine mono- and diimides, and with 1,2- and 1,4-quinones. Heterocyclic quinones are arranged in this chapter according to the ring size of the heterocyclic part and the number of heteroatoms present. Extended quinones, i.e., benzo- naphtho-, and quinones with two heterocyclic rings, are discussed after the simple, parent representatives.