Synthesis of Enantiopure 2‑<i>C</i>‑Glycosyl-3-nitrochromenes

Abstract

A novel methodology has been developed to obtain enantiopure 2-<i>C</i>-glycosyl-3-nitrochromenes. First, (<i>Z</i>)-1-bromo-1-nitroalkenes were prepared from the corresponding sugar aldehydes through a sodium iodide-catalyzed Henry reaction with bromonitromethane followed by elimination of the resulting 1-bromo-1-nitroalkan-2-ols. In the next step, reaction of the sugar-derived (<i>Z</i>)-1-bromo-1-nitroalkenes with <i>o</i>-hydroxybenzaldehydes afforded enantiopure (2<i>S</i>,3<i>S</i>,4<i>S</i>)-3-bromo-3,4-dihydro-4-hydroxy-3-nitro-2<i>H</i>-1-benzopyrans, which, upon SmI₂-promoted β-elimination, yielded chiral enantiopure 2-<i>C</i>-glycosyl-3-nitrochromenes