Novel stereoselective synthesis of the spiroketal structure using Pd(II) catalyst and application to the synthesis of natural products

We have developed highly stereoselective intamolecular cyclization of dihydroxyketone using palladium(II) catalyst via hemiacetal, in which cyclization occurs without activation of the allylic alcohol to afford spiroketal structures. We have also synthesized some monosaccharide such as D-ribose and deoxy-D-ribose used by this cascade cyclization. And we succeed in the stereoselective synthesis of spiroketal structures of spirofungin A and bistramide A.