Synthetic studies on lemonomycin: construction of the tetracyclic core

A substrate-induced stereocontrol strategy was used to gain access to the tetracyclic core of (−)-lemonomycin. An advanced intermediate was prepared from a known substituted tyrosinol through a 16-step sequence, which involved a Pictet-Spengler reaction, a [3+2] dipolar cycloaddition and an enamide hydrogenation.