The first construction of a 3,6-bridged ellagitannin skeleton with 1C4/B glucose core; synthesis of nonamethylcorilagin

The synthesis of nonamethylcorilagin is described. In the synthesis, the intramolecular Ullmann coupling afforded the (R)-hexahydroxydiphenoyl part––a characteristic bridge structure of the target molecule––when the glucopyranose ring was opened in advance. This synthesis demonstrates the first synthetic approach to a 3,6-bridged ellagitannin skeleton whose conformation of the d-glucose core is 1C4 or skew boat.