Lewis acid-catalyzed ring-opening reactions of semicyclic N,O-acetals.

[figure: see text] Ring-opening reactions of semicyclic N,O-acetals with various nucleophiles such as silyl enol ethers are effectively catalyzed by a Lewis acid (TMSOTf). Reactions of 3-substituted N,O-acetals showed high diastereoselectivities. Synthetic utility of this method has been demonstrated in the stereoselective synthesis of an anti-malarial agent, isofebrifugine.