Denmark Scott E, Baiazitov Ramil Y
Department of Chemistry, Roger Adams Laboratory, University of Illinois, Urbana, Illinois 61801, USA.
J Org Chem. 2006 Jan 20;71(2):593-605. doi: 10.1021/jo052001l.
[reaction: see text] Two model studies in support of a total synthesis of the complex polycyclic alkaloid daphnilactone B have been completed. The objectives of the models studies were to demonstrate the use of a tandem double-intramolecular [4+2]/[3+2] nitroalkene cycloaddition for the stereocontrolled construction of four of the rings in the core of the natural product. The first model study established the ability to create a pyrrolidine ring corresponding to ring A of daphnilactone B through a modification of the dipolarophile and subsequent functional group manipulations. The second model study required the modification of the dienophile in the [4+2] cycloaddition to accommodate the formation of a piperidine ring (ring B of daphnilactone B). Nitroalkene 26 containing a diene as the dienophile served well in the tandem cycloaddition to afford the nitroso acetal 38a in 77% yield. Subsequent functional group manipulations allowed for the high-yielding conversion to the core of daphnilactone B.
[反应：见正文] 两项支持复杂多环生物碱瑞香内酯B全合成的模型研究已完成。模型研究的目的是证明使用串联双分子内[4+2]/[3+2]硝基烯烃环加成反应来立体控制构建天然产物核心中四个环。第一项模型研究通过亲偶极体的修饰及随后的官能团操作，确立了构建与瑞香内酯B的A环相对应的吡咯烷环的能力。第二项模型研究要求在[4+2]环加成反应中修饰亲双烯体，以适应哌啶环（瑞香内酯B的B环）的形成。含有二烯作为亲双烯体的硝基烯烃26在串联环加成反应中表现良好，以77%的产率得到亚硝基缩醛38a。随后的官能团操作实现了向瑞香内酯B核心的高产率转化。
