Three‐Step Synthesis of Sialic Acids and Derivatives

Flexible yet efficient: Sialic acids such as L-N-acetylneuraminic acid (see picture) can be synthesized in only three steps by 1) vinylation of an aldose through a modified Petasis coupling reaction, 2) 1,3-dipolar cycloaddition with a nitrone to construct an isoxazolidine ring, and 3) base-catalyzed β elimination/ring opening of the isoxazolidine to generate a γ-hydroxy-α-keto acid.