Synthesis of (±)-4-deoxypodophyllotoxin, (±)-podophyllotoxin and (±)-epipodophyllotoxin
作者:David W. Jones、Adrian M. Thompson
DOI:10.1039/p19930002541
日期:——
the C-2 exo-CO2Me adduct 4 which is transformed in four steps into epipodophyllotoxin 10a. Attempted addition of dimethyl maleate to 1 proceeds with decarboxylation of the putative endo-adduct 11 to a transient o-quinodimethane which undergoes a highly regioselective 1,5-hydrogen shift to the dihydronaphthalene 14. The alternative 1,5-shifts are shown for the model o-quinodimethane 22[22 and 22a(arrows)]
6,7-亚甲基二氧基-1-(3',4',5'-三甲氧基苯基)-2-苯并吡喃-3-酮1和富马酸二甲酯在乙腈中的转化率主要为C-2 exo -CO 2 Me加合物4分四步将表鬼臼毒素10a注入。尝试将马来酸二甲酯添加至1时,将推定的内加合物11脱羧为瞬态邻喹啉甲烷,后者会发生高度区域选择性的1,5-氢转移至二氢萘14。显示了邻喹啉甲烷模型22的替代1,5-移位22 [ 22图22a和22a(箭头)]表明其中显示的空间冲突不利于22a的移动。在有效的反应序列中,产物14被转化为4-脱氧鬼臼毒素,该反应具有关键步骤,即醛26至27的高产率差向异构化。二氢萘14也被转化为鬼臼毒素10b(七个步骤,总收率24%);新颖的步骤包括的差向异构化35至36和选择氧化34到35使用(BU 3 Sn)的2 O-i 2。