Natural product syntheses using biaryl coupling reactions

The intramolecular aryl-Aryl coupling reaction of phenyl benzoate derivatives is a convenient method for construction of a 6H-dibenzo[M]pyran-6-one skeleton which is frequently found in natural products. Palladium reagents are used for the C-C bond formation between two aromatic rings. This review article describes that this technique is effective for the syntheses of several natural products possessing a highly oxygenated 6H-dibenzo[M]pyran-6-one core. The regiose- lectivity in the reaction is also discussed with some transition state illustrations. For further appli-cation, asymmetric construction of the biphenyl moiety is presented using the dynamic kinetic optical resolution method. In the latter part, the biphenyl synthesis and the diphenyl ether synthesis under the Ullmann conditions are described toward the total synthesis of ellagitannins. The syntheses of several important part structures of ellagitannins are illustrated using the Ullmann reactions. Finally, one example of the total synthesis of ellagitannin is demonstrated.