Synthesis and Properties of First and Second Generation Chiral Dendrimers with Triply Branched Units: A Spectacular Case of Diastereoselectivity
作者:Peter K. Murer、Jean-Marc Lapierre、Guy Greiveldinger、Dieter Seebach
DOI:10.1002/hlca.19970800522
日期:1997.8.11
center-piece triols, 3 and 4, would smoothly react to give the desired dendrimers (e.g., 44, and 46-49) and others would not, with the reactions stopping at the dendritic alcohols containing only two branches (e.g., 45, and 50-53; see Schemes 4 and 5). Considering the distance at which the intermediate diastereoisomeric ‘doubly coupled’ dendritic alcohols differ in their configuration, this diastereodifferentiation
没有(3-5)和具有脂肪族(6)或芳香族(7)延伸单元的手性三醇(可能被认为是三(羟甲基)甲烷的衍生物),以及第一代和第二代苄基支化溴化物,17 ,18,23,24,29,和30经受威廉森醚化条件下(将NaH在THF中)。这给了第一“完全手性”树枝状聚合物,具有三重分支和在每个立体中心和每一个分支点(包括中央积木:见33-42,44,和46-49)。无法制备高于第二代的此类树状聚合物。非对映异构第二代的某些组合支溴化物,23,24,29,和30,和对映体中心件三醇,3和4,将反应顺利,得到所需的树枝状聚合物(例如,44,和46-49)和其他不会,与反应在仅含有两个分支的树枝状醇停止(例如,45,和50-53 ;参见方案4和5)。考虑到中间非对映异构体“双偶联”树枝状醇的构型不同,这种非对映异构或分子识别现象(通过尝试在2 39个可能的非对映异构体中仅制备8个而发现!)是最令人惊讶的结果。所