作者:Jun'ichi Uenishi、Reiko Kawahama、Osamu Yonemitsu
DOI:10.1021/jo961993f
日期:1997.3.1
(-)-Ircinianin (1), a cyclic furanosesterterpenetetronic acid isolated from a marine sponge (genus Ircinia), is synthesized in 17 steps from (S)-2-methylpropane-1,3-diol mono THP ether 10 and 3-furfural. The key step involves a NiCl2-CrCl2-mediated coupling reaction of iodotriene 9 with chiral aldehyde 8 in DMSO and subsequent intramolecular Diels-Alder reaction in one pot. Both reactions proceed very smoothly at room temperature and eventually give the cyclic product 30A possessing the desired cyclic skeleton of 1 in 60% yield. The structure of 30A is determined by X-ray crystallographic analysis. The stereochemistry of Diels-Alder reactions of 7A and another acyclic precursor 7B are discussed. The first total synthesis of(+)-wistarin (2) is accomplished in 55% yield by iodoether ring formation of 1 and hydrogenolysis of the iodide 33A. Based on the coupling constant in the proton NMR spectrum of 33A, the reported structure 2A is revised to 2B.
(-)-Ircinianin (1),一种从海海绵(Ircinia属)中分离出的环状糠酸酯倍半萜四烯酸,通过(S)-2-甲基丙烷-1,3-二醇单THP醚(10)和3-糠醛在17步反应中合成。关键步骤涉及在DMSO中,NiCl₂-CrCl₂介导的碘代三烯(9)与手性醛(8)之间的偶联反应,随后在同一锅中进行分子内Diels-Alder反应。这两个反应在室温下进行得非常顺利,最终以60%的收率得到环状产物30A,其具有目标化合物1所需的环状骨架。通过X射线晶体学分析确定了30A的结构。讨论了Diels-Alder反应中7A和另一个非环前体7B的立体化学。通过1和碘醚环的形成以及碘化物33A的氢解,首次完成了(+)-wistarin (2)的全合成,产率为55%。根据33A的¹H NMR光谱中的偶合常数,对报道的结构2A进行了修订,最终结构为2B。