Covering: 1997 to early 2003

Recent studies on enzymes catalyzing the Diels–Alder reaction, often named “Diels–Alderases”, clearly demonstrated the involvement of this synthetically useful reaction in the biosynthesis of natural products. This review covers natural Diels–Alder type cycloadducts, synthetic efforts on the chemical feasibility of the biosynthetic Diels–Alder reaction and a brief history of studies on Diels–Alderases. In addition, reaction mechanisms of artificial and natural Diels–Alderases are discussed.