A series of aromatic cyanohydrins and their O silyl ethers have been synthesized by trimethylsilylcyanation of aromatic aldehydes using a catalyst generated in situ from optically active R (+) 1,1 2 bisnaphthol with...A series of aromatic cyanohydrins and their O silyl ethers have been synthesized by trimethylsilylcyanation of aromatic aldehydes using a catalyst generated in situ from optically active R (+) 1,1 2 bisnaphthol with n butyl lithium. Mandelonitrile was prepared in an isolated yield 70% with more than \{e.e.\} =60%. The effect of solvents and the amount of catalyst on enantioselectivity was also investigated.展开更多
High performance liquid chromatography coupled with quadruple-time-of-flight mass spectrometry(HPLC-Q-TOF-MS)method was developed for analyzing the hydrolytic mixtures of ginsenoside R_(g1) in acidic conditions(pH 3)....High performance liquid chromatography coupled with quadruple-time-of-flight mass spectrometry(HPLC-Q-TOF-MS)method was developed for analyzing the hydrolytic mixtures of ginsenoside R_(g1) in acidic conditions(pH 3). Three catalysts, a heteropolyacid(H_4SiW_(12)O_(40), SiW_(12) for short), its complex with γ-CD(SiW_(12)/γ-CD for short) and formic acid, were used for comparison. The chemical transformation products were identified based on the accurate mass measurement and the fragment ions obtained from tandem mass spectrometry. It was concluded that the catalytic efficiency of SiW_(12)(≈SiW_(12)/γ-CD) is ca. 410 times higher than that of formic acid, thus becoming the most efficient catalyst for chemical transformations of ginsenosides.展开更多
文摘A series of aromatic cyanohydrins and their O silyl ethers have been synthesized by trimethylsilylcyanation of aromatic aldehydes using a catalyst generated in situ from optically active R (+) 1,1 2 bisnaphthol with n butyl lithium. Mandelonitrile was prepared in an isolated yield 70% with more than \{e.e.\} =60%. The effect of solvents and the amount of catalyst on enantioselectivity was also investigated.
基金supported by the National Natural Science Foundation of China(21371025),the 111 Project(B07012)the degree and postgraduate education development research project(YJYJG2015B07)by Beijing Institute of Technology
文摘High performance liquid chromatography coupled with quadruple-time-of-flight mass spectrometry(HPLC-Q-TOF-MS)method was developed for analyzing the hydrolytic mixtures of ginsenoside R_(g1) in acidic conditions(pH 3). Three catalysts, a heteropolyacid(H_4SiW_(12)O_(40), SiW_(12) for short), its complex with γ-CD(SiW_(12)/γ-CD for short) and formic acid, were used for comparison. The chemical transformation products were identified based on the accurate mass measurement and the fragment ions obtained from tandem mass spectrometry. It was concluded that the catalytic efficiency of SiW_(12)(≈SiW_(12)/γ-CD) is ca. 410 times higher than that of formic acid, thus becoming the most efficient catalyst for chemical transformations of ginsenosides.
