Synthesis and biological activity of cyanobacterial aeruginosins

In this thesis, the chemical synthesis and biological activity of aeruginosins are described. Aeruginosins are a class of secondary metabolites produced by cyanobacteria. Cyanobacteria belong to the oldest living organisms on Earth, capable of inhabiting the most remote and hostile areas.
Chapter I: Over the past years, an augmentation of harmful algal blooms (HABs) has been observed in waters all over the world. HABs pose a threat for animals and humans alike. In the past, the research focus was mainly laid on the investigation of the toxicity of microcystins and nodularins. Recent results showed that also chlorinated and sulfated aeruginosins such as 828A have to be considered as cyanotoxins. In this chapter, the successful synthesis of four congeners of aeruginosin 828A bearing different permutations of the chlorine and sulfate substituents is reported. Performed toxicity tests against the crustacean Thamnocephalus platyurus indicate that especially the sulfate group exerts a notable influence on the toxicity of the aeruginosins.
Chapter II: In this chapter, the results of a purely synthetically driven research project are described. The efforts which were taken in order to elucidate strategies towards the total synthesis of the recently isolated aeruginosin KT608A are summarized. Two novel synthetic approaches were developed for the preparation of the D-diepi-Choi core structure present in KT608A. Substantial differences in the NMR spectral data between the synthetic material and the isolated natural product resulted in proposing a revised structure for aeruginosin KT608A.