Reactivity of 2‑Nitropyrrole Systems: Development of Improved Synthetic Approaches to Nitropyrrole Natural Products

Fundamental study of the reactivity of 2-nitropyrrole systems has enabled the identification of effective methods for incorporation of this unusual motif into advanced natural product frameworks. The presence of electron-rich pyrrole N-protecting groups (BOM, Boz) was demonstrated to enable a variety of previously unsuccessful palladium-mediated cross-couplings to be carried out in high yield. Based on this foundation, a series of regio- and stereoselective synthetic routes toward the nitropyrrolin and heronapyrrole families of natural products was developed by our group (G1–3). A full account of the strategic evolution of these approaches is reported here, highlighting the details of the setbacks encountered and eventual successes achieved en route, including the total synthesis of heronapyrrole B. The fundamental studies and completed total syntheses provide general access to the bioactive 2-nitropyrrole natural product manifold and also establish practical and efficient methods for preparation and elaboration of the medicinally relevant 2-nitropyrrole motif