Concise synthesis of zanamivir and its C4-thiocarbamido derivatives utilizing a [3+2]-cycloadduct derived from d-glucono-δ-lactone

A concise synthesis of zanamivir (GG167, 1) has been accomplished utilizing the adduct of a highly diastereoselective 1,3-dipolar cycloaddition between methyl acrylate and the nitrone derived from d-glucono-δ-lactone. Azide-free introduction of C4 nitrogen functionality and one-pot selective O-acetylation followed by straightforward generation of dihydropyran moiety are two advantages in this synthesis. Using the established methodology and common intermediate, two representative C4-thiocarbamido derivatives of zanamivir were also synthesized.