Formal Asymmetric Synthesis of Pentalenolactone E and Pentalenolactone F-1. Retrosynthesis and π-Facial Differentiation in Palladium-Catalyzed and Dipolar [3 + 2]-Cycloaddition Reactions of Bicyclic Alkenes: Evidence for Electrostatic Control of Stereoselectivity
作者:Bernd Rosenstock、Hans-Joachim Gais、Eva Herrmann、G. Raabe、Paul Binger、Andreas Freund、Petra Wedemann、Carl Krüger、Jörg Lindner
DOI:10.1002/(sici)1099-0690(199802)1998:2<257::aid-ejoc257>3.0.co;2-z
日期:1998.2
in which the hydroxy group occupies the pseudoaxial position, to be the more stable one. According to force-field calculations, the 5E-conformation seems to be stabilized by an intramolecular electrostatic interaction between the hydroxylic oxygen atom and the lactone carbonyl group, corresponding to the initial step of an intermolecular nucleophilic attack at the carbonyl group. The O−C1 distance and
已成功开发了戊二酸内酯E(2a)和戊二酸内酯F(2b)的不对称合成成功的新策略。此策略涉及的环的组件A 2A和2B通过冰儿型Pd催化[3 + 2] diquinene的-环反应7与二苯基-取代的亚甲基环丙烷18。通过使用猪肝酯酶催化的对映选择性水解作为关键步骤,可从二酯8分8个步骤以对映体纯净状态获得对苯二酚7。1,3-偶极和Pd催化的[3 + 2]-环加成反应以及7的Michael反应的非预期的面部选择性已经观察到。因此,7与CH 2 N 2以98%或更高的立体选择性反应,有利于在凹侧发生反应,并形成了顺式三环烷27。Trost型Pd催化7与11的反应,根据溶剂的极性,比例为1:1.7至1:5.3的全反式三奎烷6和顺式三奎烷12。7与亚甲基环丙烷(13)在甲苯中经Binger型Pd催化的环加成反应,以1:7的比例提供6和12的混合物。在Pd催化的反应中在具有苯基取代的亚甲基环丙烷14a /