The First Total Synthesis of (–)-Lemonomycin and Progress toward the Total Synthesis of (+)-Cyanocycline A

Abstract

The first total synthesis of (–)-lemonomycin has been accomplished. The synthesis features a novel, auxiliary-controlled asymmetric dipolar cycloaddition, a highly convergent Suzuki coupling, a diastereoselective enamide hydrogenation to set the C(3) stereochemistry, and a convergent, efficient, and completely diastereoselective Pictet-Spengler cyclization with a glycosyloxy acetaldehyde. The total synthesis of (+)-cyanocycline A has been approached along two routes. Both routes feature dipolar cycloaddition reactions with alkyne-containing substrates and completely diastereoselective hydrogenations to set the C(4) stereochemistry. Proposals for the advancement of late-stage intermediates to the natural product are included.