Efficient Rhodium-Catalyzed Conjugate Addition of Arylboronic Acids to Unsaturated Furano Esters for the Highly Stereoselective Synthesis of Four Natural Trisubstituted Furanolignans
(±)-sanshodiol methyl ether (1c) and (±)-acuminatin methyl ether (1d), were prepared stereoselectively in five steps from a 4-(arylmethylene)-2-methoxytetrahydrofuran derivative obtained by a MCR reaction. The key step of this synthesis is the microwave-assisted stereoselective addition of a boronic acid (Hayashi–Miyaura reaction) to a 4-ethoxycarbonyldihydrofuran, generating three contiguous stereogenic centers