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

用双(乙腈)氯化钯(II)处理含烯丙基醇的光学活性氨酯的分子内环化反应，使反(2，6)哌啶体系成为单一的非对映异构体。在这些转化过程中，Pd(II)物种不会被还原，因此催化剂可以循环使用，而不需要重新氧化。另一方面，含烯丙基氯的模拟底物在氢化钠存在下用三氟乙酸银环合得到了顺式(2，6)哌啶体系。用这些过渡金属络合物对其他底物进行了环化反应，得到了类似的结果。所得到的环加合物分别转化为(+)-Prosopinine、(-)-SS20846A、(+)-脱氧甘露糖苷和(-)-羟基西丹明，是有用的手性构建块

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