The Synthesis of Melohenine B and a Related Natural Product

A concise synthesis of melohenine B and O-ethyl-14-epimelohenine B, from eburnamonine, was achieved via a biomimetic diastereoselective singlet oxygen-mediated oxidative cleavage of the indole C2-C7 bond. These studies enabled the assignment of the absolute configuration of the natural products. In line with a proposed biosynthetic pathway, the resulting nine-membered ring containing products could be converted to the corresponding quinolones.