Efficient synthesis of γ-DDB

Synthesis of γ-DDB, which is another family member of α-DDB (dimethyl 4,4′-dimethoxy-5,6,5′,6′- dimethylenedioxybiphenyl-2,2′-dicarboxylate), is described. The unsymmetric isomer (γ-DDB) was constructed by a linker-directed intramolecular Ullmann coupling reaction, followed by the cleavage of the linker and re-esterification.