Synthesis of branched iminosugars through a hypervalent iodine(III)-mediated radical-polar crossover reaction

The synthesis of a novel type of branched iminosugars is described. This synthetic strategy is based on two key reactions: first, an aldol reaction with formaldehyde in order to introduce selectively the hydroxymethyl branch, and second, a tandem β-fragmentation-intramolecular cyclization reaction. The combination of both reactions afforded a battery of compounds exhibiting a great structural complexity, with the concomitant formation of a quaternary center, starting from readily available aldoses. With this approach we have demonstrated the usefulness of the fragmentation of anomeric alkoxyl radicals (ARF) promoted by the PhIO/I2 system for the preparation of new compounds with potential interest for both medicinal and synthetic chemists.This work was supported by the Gobierno de Canarias (Research Program ProID20100088) and the investigation program no. CTQ2007-67492/BQU of the Ministerio de Educación y Ciencia (Spain) cofinanced with the Fondo Europeo de Desarrollo Regional (FEDER). A.G.S. thanks the I3P-CSIC Program for a fellowshipPeer Reviewe