A wide variety of secondary amines are chemoselectively subjected to N-nitrosation reaction with treatment of citric acid and NaNO2 in the presence of wet SiO2 （50%, w/w） in dichloromethane at room temperatture unde...A wide variety of secondary amines are chemoselectively subjected to N-nitrosation reaction with treatment of citric acid and NaNO2 in the presence of wet SiO2 （50%, w/w） in dichloromethane at room temperatture under heterogeneous conditions. The Nnitrosation method is very simple and products can be easily isolated with good to high yields.展开更多
The in vitro effects of baicalein,wogonin,baicalin and Na_2MoO_4 on N-nitrosation reaction have been studied. The N-nitrosation reaction has been determined by the amount of dimethylnitrosamine(DMN) and diethylnitrosa...The in vitro effects of baicalein,wogonin,baicalin and Na_2MoO_4 on N-nitrosation reaction have been studied. The N-nitrosation reaction has been determined by the amount of dimethylnitrosamine(DMN) and diethylnitrosamine(DEN) produced using the UV-photclysis spectrophotometric and pyrolysis gas chromatography test. Baicalein,wogonin and Na_2MoO_4 showed varing extents of inhibition of the formation of DMN and DEN. Baicalin promoted the formation of DMN and DEN under the condition of simulating gastric Juices. It is also found that E. coli showed a remarkable promoting effect on the formation of DMN and DEN,but this promoting effect could be blocked to some extent by baicalein,wogonin,baicalin and Na_2MoO_4. Besides, Na_2MoO_4 and wogonin have shown synergic effect on the blocking of N-nitrosation reaction.展开更多
Reactive nitrogen oxygen species（RNOS） implicate damage in biological systems,especially leading to inflammation,neurodegenerative and cardiovascular diseases,and cancer by altering the functions of biomolecules thr...Reactive nitrogen oxygen species（RNOS） implicate damage in biological systems,especially leading to inflammation,neurodegenerative and cardiovascular diseases,and cancer by altering the functions of biomolecules through the N-nitrosation and N-nitration reactions.The mechanisms of N-nitrosation and N-nitration reactions of ammonia and dimethylamine by RNOS,i.e.,N2O3,N2O4,N2O5 and ONOOH,were investigated at the CBS-QB3 level of theory.The computational results indicate that the N-nitrosation reaction prefers a concerted mechanism,in which a H-abstraction and ON-addition occur simultaneously,whereas a stepwise mechanism（also called a free radical mechanism） is more favorable for most nitrating agents in the N-nitration reaction,where NO2 first abstracts a hydrogen atom from the nitrogen of amines and then the induced intermediate reacts with NO2 once more to form the nitration products.However,the concerted pathway is still a feasible process for some nitrating agents such as N2O5.In addition,the relationship between the structures of different RNOS and their nitrosating or nitrating abilities was also investigated.展开更多
基金support for this work by the research affairs of Ilam University,Ilam,Iran
文摘A wide variety of secondary amines are chemoselectively subjected to N-nitrosation reaction with treatment of citric acid and NaNO2 in the presence of wet SiO2 （50%, w/w） in dichloromethane at room temperatture under heterogeneous conditions. The Nnitrosation method is very simple and products can be easily isolated with good to high yields.
文摘The in vitro effects of baicalein,wogonin,baicalin and Na_2MoO_4 on N-nitrosation reaction have been studied. The N-nitrosation reaction has been determined by the amount of dimethylnitrosamine(DMN) and diethylnitrosamine(DEN) produced using the UV-photclysis spectrophotometric and pyrolysis gas chromatography test. Baicalein,wogonin and Na_2MoO_4 showed varing extents of inhibition of the formation of DMN and DEN. Baicalin promoted the formation of DMN and DEN under the condition of simulating gastric Juices. It is also found that E. coli showed a remarkable promoting effect on the formation of DMN and DEN,but this promoting effect could be blocked to some extent by baicalein,wogonin,baicalin and Na_2MoO_4. Besides, Na_2MoO_4 and wogonin have shown synergic effect on the blocking of N-nitrosation reaction.
基金supported by the National Natural Science Foundation of China (No 20672011)Beijing Natural Science Foundation (No 2092008)Beijing Nova Program (No 2008B09)
文摘Reactive nitrogen oxygen species（RNOS） implicate damage in biological systems,especially leading to inflammation,neurodegenerative and cardiovascular diseases,and cancer by altering the functions of biomolecules through the N-nitrosation and N-nitration reactions.The mechanisms of N-nitrosation and N-nitration reactions of ammonia and dimethylamine by RNOS,i.e.,N2O3,N2O4,N2O5 and ONOOH,were investigated at the CBS-QB3 level of theory.The computational results indicate that the N-nitrosation reaction prefers a concerted mechanism,in which a H-abstraction and ON-addition occur simultaneously,whereas a stepwise mechanism（also called a free radical mechanism） is more favorable for most nitrating agents in the N-nitration reaction,where NO2 first abstracts a hydrogen atom from the nitrogen of amines and then the induced intermediate reacts with NO2 once more to form the nitration products.However,the concerted pathway is still a feasible process for some nitrating agents such as N2O5.In addition,the relationship between the structures of different RNOS and their nitrosating or nitrating abilities was also investigated.
