Borane adducts of punicine and of its dehydroxy derivatives (pyridinium-1-yl)-2- and 3-phenolates
作者:Christian F. Otto、Colin Herzberger、Ming Liu、Jan C. Namyslo、Martin Nieger、Tyll Freese、Felix Lederle、Eike G. Hübner、Andreas Schmidt
DOI:10.1016/j.tet.2020.131627
日期:2020.11
The natural product punicine (Punica granatum) exists in two tautomeric forms, the cross-conjugated mesomeric betaine 1-(pyridinium-1-yl)-2-hydroxy-phenyl-5-olate and the conjugated mesomeric betaine 1-(pyridinium-1-yl)-5-hydroxy-phenyl-2-olate. Punicine as well as its picoline derivatives reacted with tris(pentafluorophenyl)borane exclusively at the 2′-olate group to form zwitterionic borates. Correspondingly
天然产物矮牵牛(Punica granatum)以两种互变异构形式存在:交叉共轭美索美甜菜碱1-(吡啶-1-基)-2-羟基-苯基-5-油酸酯和共轭美索美甜菜碱1-(吡啶-1-1) -基)-5-羟基-苯基-2-油酸酯。Punicine及其甲基吡啶衍生物仅在2'-olate基团上与三(五氟苯基)硼烷反应形成两性离子硼酸酯。相应地,矮牵牛的5'-脱羟基衍生物,共轭的杂环美麦酸甜菜碱1-(吡啶-1-基)-苯基-2-油酸酯及其甲基吡啶衍生物也产生了硼酸酯,而交叉共轭异构体2'的类似反应-脱羟基石榴碱[1-(吡啶-1-基)-苯基-3-油酸酯]没有形成稳定的加合物。