Organic synthesis is as highly developed, versatile, and interdisciplinary branch of natural science. Modern synthetic methods have been developed to allow us the preparation of complex molecules and new materials with unique properties. The accomplishments discussed in this thesis including the following: (1) The convergent and stereoselective total synthesis of paulownin using the type II photocyclization reaction. (2) The efficient synthesis of aklavinone antibiotic utilizing a photoenolization/Diels-Alder reaction and palladium-catalyzed aromatization sequence. (3) A direct synthetic approach to the pleurotin anticancer agent featuring the photoenolization and highly stereoselective intramolecular Diels-Alder reactions, and the finding of the new lead in the discovery of therapeutic anticancer agents.