Sessiline is an alkaloid which is recently isolated from the fruits of Acanthopanax sessiliflorus. The molecule contains two five-membered heterocyclic units joined together by an acylaminocarbinol-ether type bond. He...Sessiline is an alkaloid which is recently isolated from the fruits of Acanthopanax sessiliflorus. The molecule contains two five-membered heterocyclic units joined together by an acylaminocarbinol-ether type bond. Here, we describe the first, simple synthesis of sessiline from 5-hydroxypyrrolidin-2-one and 5-hydroxymethylfurfural, which are prepared from succinimide and furfuryl alcohol, respectively. The coupling reaction takes place on moderate heating under neat conditions.展开更多
The dissociation chemistry of primary fragment ions from the protonated proline-containing tripeptides glycylprolylglycine,prolylglycylglycine,and prolylprolylglycine was investigated by electrospray ionization multi-...The dissociation chemistry of primary fragment ions from the protonated proline-containing tripeptides glycylprolylglycine,prolylglycylglycine,and prolylprolylglycine was investigated by electrospray ionization multi-stage mass spectrometry.Calcula-tions showed the a 2 ions generated from b 2 ions were cyclic,which is energetically more favorable than the linear form.The prolyl residue in the structure affected the energy hypersurface of the dissociation reaction from the b 2 ion to the a 2 ion.In the fragmen-tation of a 2 ions,the iminium-imine complex corresponding to loss of CO from the a 2 ion was suggested to be an ion-neutral com-plex (INC).The a 1 ion was generated from direct separation of this INC,and the internal iminium ion,which was absent in PGG,was generated from another INC that was formed from the first INC via proton-bridged complex-mediated intramolecular proton transfer.Although these intermediates are unstable,their existence is supported by experiments and density functional theory calculations.展开更多
报道手性合成砌块(4S,5R)-N-苄基-4-苄氧基-5-羟甲基-2-吡咯烷酮(3a)的直接还原氰基化及产物的立体化学与转化研究.含未保护羟基的内酰胺用Li Al H4/KCN体系直接还原氰基化,生成比例为69∶31的2,5-反式/顺式非对映立体异构体.与文献类...报道手性合成砌块(4S,5R)-N-苄基-4-苄氧基-5-羟甲基-2-吡咯烷酮(3a)的直接还原氰基化及产物的立体化学与转化研究.含未保护羟基的内酰胺用Li Al H4/KCN体系直接还原氰基化,生成比例为69∶31的2,5-反式/顺式非对映立体异构体.与文献类似结果对比显示,氰基负离子对5-羟甲基-(35)-1-吡咯啉鎓中间体的加成主要受立体电子效应和C(5)位取代基(羟甲基)与进攻试剂间烯丙型1,3-位阻控制.该混合物在碱性条件下水解,生成比例为10∶90的2,5-反式/2,5-顺式-bulgecinine衍生物.这一结果表明氰基水解反应伴随着在C(2)位发生了有合成价值的串联差向异构化.由此建立了立体选择性地合成2,5-顺式(-)-N-甲基-2-别-bulgecinine的简便方法.展开更多
文摘Sessiline is an alkaloid which is recently isolated from the fruits of Acanthopanax sessiliflorus. The molecule contains two five-membered heterocyclic units joined together by an acylaminocarbinol-ether type bond. Here, we describe the first, simple synthesis of sessiline from 5-hydroxypyrrolidin-2-one and 5-hydroxymethylfurfural, which are prepared from succinimide and furfuryl alcohol, respectively. The coupling reaction takes place on moderate heating under neat conditions.
基金supported by China National Funds for Distinguished Young scientists(21025207)the National Natural Science Foundation of China(20975092)the Zhejiang Provincial Natural Science Foundation of China(Y4100020)
文摘The dissociation chemistry of primary fragment ions from the protonated proline-containing tripeptides glycylprolylglycine,prolylglycylglycine,and prolylprolylglycine was investigated by electrospray ionization multi-stage mass spectrometry.Calcula-tions showed the a 2 ions generated from b 2 ions were cyclic,which is energetically more favorable than the linear form.The prolyl residue in the structure affected the energy hypersurface of the dissociation reaction from the b 2 ion to the a 2 ion.In the fragmen-tation of a 2 ions,the iminium-imine complex corresponding to loss of CO from the a 2 ion was suggested to be an ion-neutral com-plex (INC).The a 1 ion was generated from direct separation of this INC,and the internal iminium ion,which was absent in PGG,was generated from another INC that was formed from the first INC via proton-bridged complex-mediated intramolecular proton transfer.Although these intermediates are unstable,their existence is supported by experiments and density functional theory calculations.
文摘报道手性合成砌块(4S,5R)-N-苄基-4-苄氧基-5-羟甲基-2-吡咯烷酮(3a)的直接还原氰基化及产物的立体化学与转化研究.含未保护羟基的内酰胺用Li Al H4/KCN体系直接还原氰基化,生成比例为69∶31的2,5-反式/顺式非对映立体异构体.与文献类似结果对比显示,氰基负离子对5-羟甲基-(35)-1-吡咯啉鎓中间体的加成主要受立体电子效应和C(5)位取代基(羟甲基)与进攻试剂间烯丙型1,3-位阻控制.该混合物在碱性条件下水解,生成比例为10∶90的2,5-反式/2,5-顺式-bulgecinine衍生物.这一结果表明氰基水解反应伴随着在C(2)位发生了有合成价值的串联差向异构化.由此建立了立体选择性地合成2,5-顺式(-)-N-甲基-2-别-bulgecinine的简便方法.
