Steroselective Intramolecular Cyclization Using Palladium Catalyst and Its Application to the Synthesis of Natsural Products

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The intramolecular cyclization of the optically active urethanes containing allylic alkohol was effected by treatment with bis(acetonitrile)palladium (II) chloride to give the trans(2,6)piperidine system as a single diastereoisomer. During these transformations, the Pd (II) species are not reduced and thus the catalyst can recycle without its reoxidation. On the other hand, cyclization of the simillar substrate containing allylic chloride using silver trifluoroacetate in the presence of sodium hydride afforded the cis(2,6)piperidine system. Cyclization of other substrates using these transition metal complexes was also examined and simillar results were obtained.The cyclo-adducts obtained were proved to be useful chiral building blocks by their conversion into (+)-prosopinine, (-)-SS20846A, (+)-Deoxymannojirimycin, and (-)-hydroxysedamine, respectively