The efficient total synthesis of bis-glycosyl apigenin from naringenin: a greener way.

An efficient total synthesis of 7-O-beta-D-glucopyranosyl-4'-O-alpha-L-rhamnopyranosyl apigenin (1) was developed in only four steps from naringenin. Compared with our previously reported first total synthesis route (six steps and 19.6% overall yield), this new route contained two steps of highly regioselective glycosylation without any selective protection steps. 7,4'-di-O-beta-D-glucopyranosyl apigenin (2) was also prepared efficiently by this method. The method is environmentally friendly, economical, and provides a greener method for flavonoid synthesis starting from an inexpensive flavanone.