Investigations of the stereoselectivity of the intramolecular Diels–Alder reaction of a spiculoic acid model system
作者:Julia S. Crossman、Michael V. Perkins
DOI:10.1016/j.tet.2008.02.109
日期:2008.5
thermally induced IMDA reactions. The configuration of C5 in the stereotriad was found to dominate any inherent endo/exo selectivity of the IMDA reaction. The isomer (2E,5S)-20 underwent the IMDA to give the spiculoic acid stereochemistry in 84% yield and 94% ds. The required stereotriads were synthesised using stereoselective substrate-controlled aldol reactions; an anti-boron aldol reaction, controlled by
制备了七水杨酸的线性模型前体,并进行了热诱导的IMDA反应。发现立体三联体中C5的构型支配了IMDA反应的任何固有的内/外选择性。对异构体(2 E,5 S)-20进行IMDA,以84%的收率和94%ds的收率得到杜仲酸的立体化学。使用立体选择性底物控制的醛醇缩合反应合成所需的立体三单元组;由(S)-2-苯甲酰氧基戊烷-3-one((S)-27)的π偏向控制的抗硼羟醛反应导致(5 R)-(22)和在手性N-酰基噻唑烷硫酮(42)的立体控制下合成钛的羟醛反应导致(5S)-(22)。使用标准的Wittig,HWE和“改性” Julia烯烃链进行的扩链安装了二烯和亲二烯体组分,从而为IMDA反应提供了线性前体。