Catalytic enantioselective alkylation of substituted dioxanone enol ethers: ready access to Calpha-tetrasubstituted hydroxyketones, acids, and esters.

The catalytic enantioselective formation of tetrasubstituted α-alkoxycarbonyl compounds is an ongoing challenge to synthetic chemists.[1] Fully-substituted α-hydroxyesters and acids comprise essential components of, and building blocks for, many bioactive natural products. These include quinic acid (1), cytotoxic leiodolide A (2),[2] and the anti-cancer agents in the harringtonine series (3a–f), whose activities depend dramatically on the presence and composition of an α-hydroxyester side-chain.[3] While many approaches to these important moieties exist,[4,5] we envisioned applying our recently developed palladium-catalyzed methods for the formation of enantioenriched all-carbon quaternary stereocenters in cyclic alkanones[6] to a general synthesis of C(α)-tetrasubstituted hydroxy carbonyl compounds.[7]