Variable Stereocontrol in Cycloadditions of 1,7,9-Decatrien-3-ones by Different Lewis Acidic Promoters – Application to a Short Synthesis of α-Eudesmol
作者:Barbara Frey、Jürgen Schnaubelt、Hans-Ulrich Reißig
DOI:10.1002/(sici)1099-0690(199906)1999:6<1385::aid-ejoc1385>3.0.co;2-v
日期:1999.6
to be highly dependent on the nature of the Lewis acid, and on the substitution pattern of the trienone substrates. Lewis acids with two coordination sites furnished predominantly the exo product trans-b via seven-membered ring chelate intermediates. The chelate-controlled intramolecular Diels–Alder reaction was then utilised as the key step in a stereocontrolled synthesis of the sesquiterpene α-eudesmol
Trienones 1 - 3进行路易斯酸促进分子内的Diels-Alder反应。结果表明,在单配位路易斯酸的情况下,环加成反应的内选择性一般较高。对于任一所述两个可能的偏好内产品顺式-一个与顺式- b,但是,被证明是高度依赖于路易斯酸的性质,并且在trienone衬底的取代模式。路易斯酸与主要提供两个配位点外产品的反式- b通过七元环螯合中间体。然后,将螯合物控制的分子内Diels-Alder反应用作倍半萜烯α-大麦醇的立体控制合成中的关键步骤。在模型三烯酮上进行的该反应模式也为合成药物上重要的天然产物二氢美维诺林铺平了道路。