Studies Toward The Asymmetric Claisen Rearrangement Of Flavonoids

Sanggenon C is one kind of flavonoids, which have anti-inflammatory effect, and also show strong antihypertensive effect in mice. This study was designed to complete the asymmetric total synthesis of Sanggenon C. From the retrosynthetic analysis route can be known that, Claisen rearrangement is one of the key steps in the process of this asymmetric synthesis. According to the literature, chiral Bronsted acids could catalyze asymmetric Claisen rearrangement, so the main contents of this experiment was to find a suitable catalyst, which could enhance reaction activity and selectivity.In this study, it is first to synthsize the model compound——3-allyl substituted flavonoids, then using this compound as substrate, going on the methodology research on the reaction conditions such as time, temperature, catalyst, solvent, etc. If a better result of the reactivity and selectivity was achieved, these mature conditions will be used to the asymmetric total synthesis of natural compound——Sanggenon C.From the experimental results it can be known that: 3-allyl substituted flavonoid was easy to synthesize. In the study of asymmetric Claisen rearrangement using this substrate, firstly we used chiral BINOL or its derivatives as ligands, boric acid as Lewis acid, for the formation of catalyst to catalyze asymmetric Claisen rearrangement, the process of which chiral boric acid should form a 6-membered hydrogen bonding chelation with the substrate. We also tried palladium, copper and other kinds of catalytic forms, no satisfactory results were obtained. So this study was decided to continue the modification on BINOL ligands for asymmetric catalysis. According to the literature searching, several ligands which can be expected to obtain a better reactivity and selectivity were designed and synthesized.It has not fully synthetic route on the asymmetric total synthesis of Sanggenon C, and also few reports on the hydrogen bonding reaction for asymmetric Claisen rearrangement. So the study of this reaction will be important for the asymmetric synthesis of Sanggenon C.