Using molecular mechanics method,values of the heat of formation (HF) of different conformations,of perylenequinonoid photosensitizes hypocrellin A (HA) and hypocrellin B (HB) were calculated and the variance of HF af...Using molecular mechanics method,values of the heat of formation (HF) of different conformations,of perylenequinonoid photosensitizes hypocrellin A (HA) and hypocrellin B (HB) were calculated and the variance of HF after phenolic protons' dissociation were calculated as well The following was found:(i) The HF values of lour conformational isomers of HA and HB are similar to each other,so the four isomcrs can transform to each other room temperature,(ii) There exists the difference between the ability of dissociation of phenolic protons of HA and that of HB,the former is higher than the latter (iii) There exist two intramolecular hydrogen bonds in HA and HB The bond energy is approximately 8 kJ/mol and the energy of conformation Ⅰ is lower than that of conformationⅡ The bond energy of HA is lower than that of HB.(iv) There exists a low energy snot when phenolic hydroxyl bond twists 180° from the position where hydrogen bond is formed,which suggests that this kind of conformation probably exists,(v) The phenolic hydrogen of HBMC forms hydrogen bond with the neighbouring nitrogen,which is its striticture basis of possessing photosensitizing activity.展开更多
通过Mitsunobu反应合成了一系列手性液晶,收率63%～71%,并通过1 H NMR、MS、IR对其结构进行了表征。结合DSC和POM研究了目标化合物的介晶性。利用Cano's wedge法研究了目标化合物的扭曲力,发现随着手性中心邻近芳环上氟原子数的增多...通过Mitsunobu反应合成了一系列手性液晶,收率63%～71%,并通过1 H NMR、MS、IR对其结构进行了表征。结合DSC和POM研究了目标化合物的介晶性。利用Cano's wedge法研究了目标化合物的扭曲力,发现随着手性中心邻近芳环上氟原子数的增多,手性液晶分子的扭曲力显著增大。实验结果表明,氟原子的引入影响了碳氧单键的自由旋转,导致手性液晶分子具有较少构象异构体,从而表现出大的扭曲力。展开更多
Here, we report a convenient and efficient synthesis strategy for the total synthesis of cyclic peptide reniochalistatin E and its conformational isomers with 32% overall yield. We found the linear peptide precursor w...Here, we report a convenient and efficient synthesis strategy for the total synthesis of cyclic peptide reniochalistatin E and its conformational isomers with 32% overall yield. We found the linear peptide precursor without side chain gave better cyclization yield.展开更多
前报从番荔枝 (Annonasquamosa)的种子中分离得一个新的环肽squaminA(cyclo [l prolyl l (S oxo) methionyl l tyrosyl l glycyl l threonyl l valyl l alanyl l isoleucyl],1)。进一步对番荔枝种子进行研究 ,发现另一个环肽 ,命名为sq...前报从番荔枝 (Annonasquamosa)的种子中分离得一个新的环肽squaminA(cyclo [l prolyl l (S oxo) methionyl l tyrosyl l glycyl l threonyl l valyl l alanyl l isoleucyl],1)。进一步对番荔枝种子进行研究 ,发现另一个环肽 ,命名为squaminB(2 ) ,用 2DNMR ,FAB MS和氨基酸分析 ,证明 2的平面结构同 1一致 ,但TLC有明显差异 ,分离得两种结晶 ,经X ray单晶衍射分析和绝对构型测定 ,确认两环肽为一对构象异构体。展开更多
基金Project supported by the National Natural Science Foundation of China
文摘Using molecular mechanics method,values of the heat of formation (HF) of different conformations,of perylenequinonoid photosensitizes hypocrellin A (HA) and hypocrellin B (HB) were calculated and the variance of HF after phenolic protons' dissociation were calculated as well The following was found:(i) The HF values of lour conformational isomers of HA and HB are similar to each other,so the four isomcrs can transform to each other room temperature,(ii) There exists the difference between the ability of dissociation of phenolic protons of HA and that of HB,the former is higher than the latter (iii) There exist two intramolecular hydrogen bonds in HA and HB The bond energy is approximately 8 kJ/mol and the energy of conformation Ⅰ is lower than that of conformationⅡ The bond energy of HA is lower than that of HB.(iv) There exists a low energy snot when phenolic hydroxyl bond twists 180° from the position where hydrogen bond is formed,which suggests that this kind of conformation probably exists,(v) The phenolic hydrogen of HBMC forms hydrogen bond with the neighbouring nitrogen,which is its striticture basis of possessing photosensitizing activity.
文摘通过Mitsunobu反应合成了一系列手性液晶,收率63%～71%,并通过1 H NMR、MS、IR对其结构进行了表征。结合DSC和POM研究了目标化合物的介晶性。利用Cano's wedge法研究了目标化合物的扭曲力,发现随着手性中心邻近芳环上氟原子数的增多,手性液晶分子的扭曲力显著增大。实验结果表明,氟原子的引入影响了碳氧单键的自由旋转,导致手性液晶分子具有较少构象异构体,从而表现出大的扭曲力。
基金supported by the National Natural Science Foundation of China(No. 21372183)Program for Innovative Teams of Outstanding Young and Middle-aged Researchers in the Higher Education Institutions of Hubei Province(No. T201702)
文摘Here, we report a convenient and efficient synthesis strategy for the total synthesis of cyclic peptide reniochalistatin E and its conformational isomers with 32% overall yield. We found the linear peptide precursor without side chain gave better cyclization yield.
文摘前报从番荔枝 (Annonasquamosa)的种子中分离得一个新的环肽squaminA(cyclo [l prolyl l (S oxo) methionyl l tyrosyl l glycyl l threonyl l valyl l alanyl l isoleucyl],1)。进一步对番荔枝种子进行研究 ,发现另一个环肽 ,命名为squaminB(2 ) ,用 2DNMR ,FAB MS和氨基酸分析 ,证明 2的平面结构同 1一致 ,但TLC有明显差异 ,分离得两种结晶 ,经X ray单晶衍射分析和绝对构型测定 ,确认两环肽为一对构象异构体。
