Redox condensations of o-nitrobenzaldehydes with amines under mild conditions - total synthesis of the Vasicinone family.

A total synthesis of the Vasicinone family of natural products from bulk chemicals was developed. Reductive condensation of o-nitrobenzaldehydes with amines utilizing iron pentacarbonyl as a reducing agent followed by subsequent oxidation leads to a great variety of polycyclic nitrogen-containing heterocycles under mild conditions. Enantiomerically pure Vasici-none, Rutaecarpine, Isaindigotone, and Luotonine were synthesized from readily available starting materials like hydroxy-proline, nitrobenzaldehyde, pyrrolidine, and piperidine in two-four operational steps without chromatography. The anti-fungal activity of all products was tested.