The Arctic sponge Haliclona viscosa as a source of a wide array of 3-alkyl pyridine alkaloids

The Arctic sponge Haliclona viscosa has proven to be a promising source for 3-alkyl pyridinium and 3-alkyl tetrahydropyridine alkaloids (3-APAs). H. viscosa was the origin of the first cyclic monomeric 3-APA (haliclocyclin F), the first cyclic trimeric 3-APA (viscosamine C), the first dimeric 3-APA amino acid adduct (viscosaline C), and the first 3aEuroalkyl tetrahydropyridine alkaloids with saturated alkyl chains (haliclamines C and D). This review focuses on the challenging structure elucidations of 3-APAs isolated from H. viscosa using a combination of NMR spectroscopy and mass spectrometry.