Concise and Stereoselective Syntheses of the Eight Natural Ant Defense Alkaloids (+)-Tetraponerine-1 to (+)-Tetraponerine-8 According to the CN(R,S) Strategy

The asymmetric syntheses of all the known defense alkaloids of the ant Tetraponera sp. tetraponerines T-1 to T-8 have been accomplished in five or six steps with 20−45% overall yields . The synthesis involved in the cross-condensation of ( R )-piperidin-2-ylacetaldehyde with 4-aminobutyraldehyde which upon quenching by cyanide ion gave a stable tricyclic amino nitrile 3 with both a high yield and complete diastereoselectivity. This amino nitrile is the common precursor of four tetraponerines. A similar synthesis using ( R )-pyrrolidine-2-ylacetaldehyde provided the tricyclic amino nitrile 2 precursor of the four other tetraponerines.