Synthesis And Antioxidant Activities Of Natural Product Xyloketals And Their Derivatives

The series of the Xyloketals are novel chromene compounds derived from mangrove entophytic fungus Xylaria sp. (#2508) from the south China coast. Those Compounds showed potent L-calcium blocking activity and inhibition of acetylcholine esterase. As a result, several research teams from both domestic and abroad have showed great interest on their total synthesis and bioactive researching.The present study focused on the total synthesis of Xyloketals compounds and their derivatives. We started with phenol compounds reacted with enol or olefin aldehyde. This reaction was carried out in the presence of toluene p-sulfonic acid, magnesium sulfate anhydrous and propionic acid. Finally, we synthesized 4 racemic Xyloketal compounds and 9 of their derivatives.Besides, we investigated the antioxidant activities of those compounds though DPPH and ABTS radical scavenging assay. The results showed that most of the compounds had radical scavenging activity. The most active compound of the DPPH assay was Compound 2-13, with the IC50 value of 7.2μmol/L and the ABTS assay was (±)Xyloketal H, with the IC50 value of 7.1μmol/L.Subsequently, the DPPH scavenging mechanism of the most active compound 2-13 was determined by Quantum Chemistry calculation method. Results showed that its phenolic hydroxyl group in position 7 is slightly more active than the one in position 5. This result may provide some guidance to the rational manual modification of Xyloketal natural products.