Gifted with novel chemical features and extraordinary biological activity, sceptrin has remained a prominent unanswered synthetic challenge since its characterization in 1981 by Faulkner and Clardy. A concise and practical solution to the myriad of chemical challenges posed by sceptrin is reported in this Communication. Thus, through a sequence involving rearrangement of an oxaquadricyclane, a new method for chemo- and regioselective halogenation, a mild sequence for 2-aminoimidazole formation, and careful synthetic choreography, (+/-)-sceptrin is obtained in a minimum of steps and in 24% overall yield from dimethyl acetylenedicarboxylate without a single use of chromatography.
Sceptrin - Enantioselective Synthesis of a Tetrasubstituted all-<i>trans</i>
Cyclobutane Key Intermediate
作者:Lena Barra、Jeroen S. Dickschat
DOI:10.1002/ejoc.201700882
日期:2017.8.24
asymmetric synthesis of both enantiomers of tetrasubstituted all-trans dimethyl 3,4-diacetylcyclobutane-1,2-dicarboxylate with high enantiomeric purity (>98 % ee) using a valine-derived chiral auxiliary in a diastereoselective photodimerization is reported. The absolute configuration was assigned by single-crystal X-ray diffraction analysis. Because this cyclobutane is a keyintermediate in the total
报道了使用缬氨酸衍生的手性助剂在非对映选择性光二聚反应中不对称合成具有高对映体纯度 (>98% ee) 的四取代全反式二甲基 3,4-二乙酰环丁烷-1,2-二羧酸酯的两种对映异构体。通过单晶 X 射线衍射分析指定绝对构型。因为这种环丁烷是 (-)-sceptrin 和ageliferin 全合成的关键中间体,我们的研究结果加强了最近修订的这些吡咯-咪唑生物碱的绝对构型。
Short, Enantioselective Total Synthesis of Sceptrin and Ageliferin by Programmed Oxaquadricyclane Fragmentation
作者:Phil S. Baran、Ke Li、Daniel P. O'Malley、Christos Mitsos