Furan-Terminated <i>N</i>-Acyliminium Ion Initiated Cyclizations in Alkaloid Synthesis
作者:Steven P. Tanis、Melissa V. Deaton、Lisa A. Dixon、Mark C. McMills、Jeffrey W. Raggon、Mark A. Collins
DOI:10.1021/jo980718l
日期:1998.10.1
cyclizations for the synthesis of linearly fused alkaloid precursors (Figure 2) is presented. The outcome of the cyclization event depends on the position of furan tether attachment (2 vs 3), tether length, and furan 5-substituent (R = H, CH(3), Ar). 3-Substituted furans cyclized to form 6- and 7-membered ring containing furans 35-38, 50, and 51 in good to excellent yields. 2-Substituted furans closed to form
提出了呋喃封端的N-酰基酰亚胺离子引发的环化用于线性融合生物碱前体合成的实用性的研究(图2)。环化事件的结果取决于呋喃系链连接的位置(2比3),系链长度和呋喃5取代基(R = H,CH(3),Ar)。3-取代的呋喃环化形成具有良好或优异收率的含呋喃35-38、50和51的6和7元环。2个取代的呋喃闭合,仅形成6元环;然而,所得产物是呋喃5-取代基的函数。5-H呋喃17和18仅产生相应的呋喃21和22,而5-CH(3)-呋喃42和43仅产生含二酮的化合物44和45。5-芳基呋喃66-71提供了呋喃的混合物-含二酮的产品72-83,其比例与苯基部分的取代有关。还讨论了表卢皮碱10的制备。