Total Synthesis as an Inspiration for Methodology Development: From Natural Products to Novel s-Tetrazines and the Study of Their Reactivity

Abstract

Total synthesis has evolved as a valuable tool for the development of novel synthetic compounds and methodologies. We report the synthetic studies towards the polycyclic, complex, marine meroterpe-noid azamerone culminating in the synthesis of two key fragments thereof. Key steps involve a three step diaminoalkylation/oxidation/condensation sequence and the cyclization of enantiomerically en-riched epoxysilanes to synthesize the cyclohexane side-chain of the natural product, with all stereo-centers set. During our synthetic approach we developed 3-bromotetrazine as a minimal tetrazine precursor for the installation of the heterocyclic pyridazine ring of the natural product. Concomi-tantly, 3-bromotetrazine proved to be a precursor for the synthesis of novel classes of 3-monosubsti-tuted s-tetrazines, as a minimal tetrazine surrogate for the installation of bio-orthogonal tetrazines in natural products and proteins and as a precursor for the synthesis of a tetrazine based chemoselective probe. Additional studies aimed at investigating its reactivity towards dienophiles, culminating in insights into the dearomatization reaction of 3-monosubstituted s-tetrazines.