Efficient Rhodium‐Catalyzed Conjugate Addition of Arylboronic Acids to Unsaturated Furano Esters for the Highly Stereoselective Synthesis of Four Natural Trisubstituted Furanolignans

Four natural lignans, (±)‐dihydrosesamin (1a), (±)‐lariciresinol methyl ether (1b), (±)‐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 with an excellent diastereoselectivity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) An efficient and stereoselective synthesis of natural lignans with three contiguousstereocenters, using a rhodium‐catalyzed,microwave‐assisted conjugate addition was developed.