Transition-Metal-Free Synthesis of C‑Glycosylated Phenanthridines via K2S2O8‑Mediated Oxidative Radical Decarboxylation of Uronic Acids

We
have developed an efficient protocol for the synthesis of C-glycosylated
phenanthridines. Tetrafuranos-4-yl and pentapyranos-5-yl radicals,
generated from K2S2O8-mediated oxidative
decarboxylation of furan- and pyranuronic acids, undergo attack to
2-isocyanodiphenyls and ensuing homolytic aromatic substitution to
provide diverse C-glycosylated phenanthridines in satisfactory yields
without resort to transition metals. This reaction tolerates various
functional groups, and enables ready synthesis of complex oligosaccharide-based
phenanthridines. The C-glycosylated phenanthridine derived from β-cyclodextrin
has been prepared, which might be potential in medicinal and biological
chemistry due to its flexible conformation.

本研究团队成功研发了一种合成C-糖基化菲类化合物的有效方法。通过K2S2O8介导的氧化脱羧反应，从呋喃和吡喃糖酸中生成四呋喃糖-4-基和五吡喃糖-5-基自由基，这些自由基攻击2-异氰基二苯基，进而发生均裂芳香取代反应，从而在不依赖过渡金属的情况下，以令人满意的产率提供多种C-糖基化菲类化合物。该反应对多种官能团具有耐受性，并可实现复杂寡糖基菲类化合物的简便合成。由β-环糊精衍生的C-糖基化菲类化合物已成功制备，由于其构象的灵活性，其在医药和生物化学领域可能具有潜在的应用价值。