The synthesis of the Securinega alkaloid secu'amamine E (ent-virosine A) has been accomplished for the first time in 12 steps and 8.5% overall yield. In addition, bubbialine has been prepared and characterized. These two alkaloids and bubbialidine, all featuring an azabicyclo[2.2.2]octane core, were rearranged to their azabicyclo[3.2.1]octane congeners, a framework found in many Securinega alkaloids. These experiments suggest that azabicyclo[2.2.2]octane derivatives could serve as intermediates in the biosynthesis of the rearranged azabicyclo[3.2.1]octane products.

Let it grow! The neuritogenic iridoid gelsemiol has been prepared in synthetic form by a radical cascade and skeletal rearrangement. This compound accelerates the differentiation of neurons and growth of neuritis (see scheme).

The synthesis of the presumed structure of aeruginosin KT608A was accomplished for the first time. The unusual d-diepi-Choi core was prepared from tyrosine via C-H activation and heterogeneous hydrogenation. Due to differences in the spectral data of synthetic and natural samples, a revised structure featuring l-diepi-Choi was proposed, which was synthesized and confirmed to be identical. On the basis of these findings, revised structures for six additional aeruginosins (KT608B, KT650, GH553, DA495A, DA511, and KB676) are presented.

Harmful algal blooms are becoming more prevalent all over the world, and identification and mechanism of action studies of the responsible toxins serve to protect ecosystems, livestock and humans alike. In this study, the chlorosulfopeptide aeruginosin 828A, which rivals in crustacean toxicity the well-known toxin microcystin LR, has been synthesized for the first time. In addition, three congeners with different permutations of the chloride and sulfate groups have been prepared, thereby allowing for toxicity studies without the risk of contamination by other natural toxins. Toxicity assays with the sensitive crustacean Thamnocephalus platyurus demonstrated that the introduction of a sulfate group leads to pronounced toxicity, while NMR spectroscopic evidence suggests that the chloride substituent modulates the conformation, which influences protease inhibitory activity.