Total Synthesis of Isohericerin, Isohericenone, and Erinacerin A: Development of a Copper-Catalyzed Methylboronation of Terminal Alkynes

Efficient and concise approaches for the synthesis of three bioactive natural products, isohericerin, isohericenone, and erinacerin A, are described in this paper. The key reactions employed include a Mannich reaction with commercially available hydroxybenzoate and subsequent one-pot lactamization to afford the common precursor isoindolinone in 3 steps and a Suzuki–Miyaura coupling reaction to connect geranyl side chains to the isoindolinone core. In addition, the mild and efficient synthesis of the C5′-oxidized geranyl side unit of isohericenone is enabled by developing a highly regioselective and efficient method for the Cu-catalyzed methylboronation of functionalized terminal alkynes.