Organocatalytic Stetter Cyclization of Pentoses for the Synthesis of Polyhydroxylated Cyclopentanone Scaffolds.

An organocatalytic approach for the carbocyclization of aldopentoses is disclosed. After initial activation, with the introduction of the intramolecular Michael acceptor in the substrate, the NHC-catalyzed Stetter reaction can be performed, giving rise to cyclopentanone scaffolds bearing multiple chiral centers and protected hydroxy groups. An optional controlled one-pot elimination provides the corresponding cyclopentenones as well. Due to the commercial availability of d- and l-pentoses all possible stereochemical permutations of the products can be prepared conveniently and affordably.