Recent Progress on Asymmetric Synthesis of Chiral Flavanones, Chromanones, and Chromenes

Flavonoids are privileged structural motifs in numerous natural products and pharmaceutical molecules, which show many biological activities such as antitumor, antioxidant, antibacterial and anti-inflammatory properties. Flavanone and chromanone which feature a chiral center are subgroups of flavonoids. The structures of flavanone and chromanone are distinct from that of flavone and chromone by a reduction of C2- C3 double bond. Deoxygenation of flavanones and chromanones provides chromenes which are also important structural motifs present in a number of natural and synthetic products that exhibit a wide range of biological activities. Besides naturally occurring flavanones, chromanone, and chromenes, the benzopyran scaffold is an important intermediate and interesting building block in organic synthesis and design of new lead compounds in drug discovery. Consequently, many attention has been paid to their efficient synthesis, especially in enantiopure forms, and many asymmetric methods for the construction of the chiral flavanone, chromanone and chromene skeletons were reported in recent years.

Keywords: Allylic Cyclization, Asymmetric Synthesis, Chromanone, Chromene, Conjugate Addition, Flavanone, Flavonoid, Reduction.