First stereospecific total synthesis of (−)-affinisine oxindole as well as facile entry into the C(7)-diastereomeric chitosenine stereochemistry

The first synthesis of (−)-affinisine oxindole was completed in an enantiospecific fashion from commercially available d-(+)-tryptophan in 10% overall yield. The asymmetric Pictet-Spengler reaction, diastereospecific oxidative-rearrangement of a tetrahydro-β-carboline, and stereospecific enolate-mediated palladium-catalyzed cross coupling process were key steps in the sequence. This represents the first example of a total synthesis via stereospecific entry into either the alstonisine related or epimeric chitosenine related oxindole stereochemistry depending on the presence or absence of an Nb-benzyl protecting group.103