Oxidation Of Hydroxycinnamic Acid Derivatives By Inorganic One-electron Oxidants

Hydroxycinnamic acid derivatives (HCAs), including ferulic acid (FA) (1), sinapic acid (SA) (2) and caffeic acid (CA) (3), are widely distributed in the plant kingdom. These compounds have been attracted considerable attention due to their various biological and pharmacological activities including antioxidative activity. It is well known that the monomeric HCAs can undergo enzymatic catalyzed oxidative cross-coupling leading to the corresponding dehydrodimers, trimers and even higher oligomers in plants. However, there have been only few reports about biological activity and oxidative cross-coupling products via chem-biomimetic synthesis of the related oligomers.In this thesis, a nonenzymatic and efficient method for the preparation of the three dilactones (8-8'-DiFA,8-8'-DiSA,8-8'-DiCA)(?) and a new FA trimer (8-O-4/8-O-4-Tri-FA) as described. It was found that 8-8'-DiFA,8-8'-DiSA and Tri-FA can be synthesized with high yields by the reaction of the corresponding monomers with Ag2O in methanol system. Otherwise,8-8'-DiCA can be efficiently obtained with CUSO4 in acetonitrile/water(v/v=1:2) system. Furthermore, the radical-scavenging activities of Hydroxycinnamic acid derivatives and their oligomers were also evaluated by using DPPH·method. It was revealed that CA and 8-8'-DiCA bearing o-dihydroxyl groups exhibited significantly higher radical-scavenging activity than those bearing no such groups, and 8-8'-DiCA was the most active one among the compounds examined.