Biomimetic syntheses of alkaloids based on tetrahydropyridine

Abstract

Many of the alkaloids found in Nitraria and Lupine species can be envisaged to arise from two simple building blocks, namely tryptamine and tetrahydropyridine. In particular in the Nitraria species, the alkaloids occur as racemates, in some cases, despite multi stereocenters. We assume that these alkaloids might be formed without interference of enzymes via spontaneous reactions of highly reactive intermediates. By carrying out a biomimetic approach many of these alkaloids were obtained via chemical synthesis, based on reactive precursors. The paper reviews the preparation of racemic Nitramine, Lupinine, Nazlinin, Nitrarine/Nitramidine, Spartein and Nitraramine from tryptamine and the trimer of tetrahydropyridine, based on imine-enamine chemistry.