Two new compounds have been isolated from methanol extract of roots of Pulsatilla chinensis(Bunge) Hegel. Their structures were established as 3-oxo-23-hydroxy-lup-20(29)-en-28-oic acid (Ⅱ) and 3-0--L-arabinopyranosy...Two new compounds have been isolated from methanol extract of roots of Pulsatilla chinensis(Bunge) Hegel. Their structures were established as 3-oxo-23-hydroxy-lup-20(29)-en-28-oic acid (Ⅱ) and 3-0--L-arabinopyranosyl-3β, 23-dihydroxylup-20(29)-en-28-oic acid (Ⅲ).展开更多
A series of new 1-aryloxyacetyl-4-aroylthiosemicarbazides were synthesized by means of solid-liguid phase transfer catalysis. The promoting effects of these new compounds on wheat growth were observed.
The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.
This paper reconstructs,based on American and Chinese primary sources,the visits of Chinese mathematicians Shiing-shen Chern陈省身(Chen Xingshen)and Hua Luogeng华罗庚(Loo-Keng Hua)4 to the Institute for Advanced Study...This paper reconstructs,based on American and Chinese primary sources,the visits of Chinese mathematicians Shiing-shen Chern陈省身(Chen Xingshen)and Hua Luogeng华罗庚(Loo-Keng Hua)4 to the Institute for Advanced Study in Princeton in the United States in the 1940s,especially their interactions with Oswald Veblen and Hermann Weyl,two leading mathematicians at the IAS.It argues that Chern’s and Hua’s motivations and choices in regard to their transnational movements between China and the US were more nuanced and multifaceted than what is presented in existing accounts,and that socio-political factors combined with professional-personal ones to shape their decisions.The paper further uses their experiences to demonstrate the importance of transnational scientific interactions for the development of science in China,the US,and elsewhere in the twentieth century.展开更多
The major products of carbonium cyclization of 1 are 2 and 3;2 is unstable and undergoes aerial oxidation to give 4.A similar product(6)from 5 is somehow stabilized by the extra ben- zoyloxy group(or OH)and can be sto...The major products of carbonium cyclization of 1 are 2 and 3;2 is unstable and undergoes aerial oxidation to give 4.A similar product(6)from 5 is somehow stabilized by the extra ben- zoyloxy group(or OH)and can be stored without deterioration.展开更多
A softening zone with recrystallized grain around the prepared crack tip in the shock waves treated C-Mn steel weld metal was observed. It is suggested that a dynamic recovery occurred around the prepared crack tip ev...A softening zone with recrystallized grain around the prepared crack tip in the shock waves treated C-Mn steel weld metal was observed. It is suggested that a dynamic recovery occurred around the prepared crack tip even at a low explosion pressure (5 GPa) because of the stress and strain concentration at the crack tip when shock waves pass through. This result supports the previous work on the improved mechanical properties of a shock treated welded joint with residual crack from the viewpoint of microstructure.展开更多
The microphase separation extent of biomedical segmented polyetherurethanes were greatly enhanced due to the presence of sulfoalkyl pendant groups contained in the hard segments,and the hard segments were more orderly...The microphase separation extent of biomedical segmented polyetherurethanes were greatly enhanced due to the presence of sulfoalkyl pendant groups contained in the hard segments,and the hard segments were more orderly aggregated through ionic interaction.展开更多
The spectral data and chemical properties of two new amides isolated from Clausena lansium led to the assignment of acyclic structures of C-6 and C-7. The absolute configurations of the two chiral carbons in C-6 were ...The spectral data and chemical properties of two new amides isolated from Clausena lansium led to the assignment of acyclic structures of C-6 and C-7. The absolute configurations of the two chiral carbons in C-6 were determined by degradation to be 3S4R.展开更多
2-Acetyl-5-methyl-2H-1,2,3—diaraphosphole 1 reacted with 2—butyne—1, 4—diol to form a tricoordinated phosphorus compound 7, which then rearranged to a novel 2, 3-disubstituted-1, 3-diene.Similar rearrangement has ...2-Acetyl-5-methyl-2H-1,2,3—diaraphosphole 1 reacted with 2—butyne—1, 4—diol to form a tricoordinated phosphorus compound 7, which then rearranged to a novel 2, 3-disubstituted-1, 3-diene.Similar rearrangement has been observed when diphenylchloropbosphine reacted with 2-butyne—1,4-diol展开更多
Intramolecular cyclization of A catalyzed by IDA in benzene or THF yields two γ-lactams through C-alkylation and one δ-and one 7-membered lactam by O-alkylation.
When the title compound was treated in protic solvent with alkali catalyses,γ-lacatam was almost the sole product.The ratio of ketone 1 to ketone 2 depended upon the reaction condition.
文摘Two new compounds have been isolated from methanol extract of roots of Pulsatilla chinensis(Bunge) Hegel. Their structures were established as 3-oxo-23-hydroxy-lup-20(29)-en-28-oic acid (Ⅱ) and 3-0--L-arabinopyranosyl-3β, 23-dihydroxylup-20(29)-en-28-oic acid (Ⅲ).
基金This project was supported by Nature Science Foundation of Gansu.
文摘A series of new 1-aryloxyacetyl-4-aroylthiosemicarbazides were synthesized by means of solid-liguid phase transfer catalysis. The promoting effects of these new compounds on wheat growth were observed.
文摘The osmium tetroxide catalyzed asymmetric dihydroxylation of the(22E)- steroidal sidechain is described and an unexpected 8:1 ratio of(22R,23R)and (22S,23S)was obtained from the(22E,24S)-24-ethyl substituted sidechain.
文摘This paper reconstructs,based on American and Chinese primary sources,the visits of Chinese mathematicians Shiing-shen Chern陈省身(Chen Xingshen)and Hua Luogeng华罗庚(Loo-Keng Hua)4 to the Institute for Advanced Study in Princeton in the United States in the 1940s,especially their interactions with Oswald Veblen and Hermann Weyl,two leading mathematicians at the IAS.It argues that Chern’s and Hua’s motivations and choices in regard to their transnational movements between China and the US were more nuanced and multifaceted than what is presented in existing accounts,and that socio-political factors combined with professional-personal ones to shape their decisions.The paper further uses their experiences to demonstrate the importance of transnational scientific interactions for the development of science in China,the US,and elsewhere in the twentieth century.
文摘The major products of carbonium cyclization of 1 are 2 and 3;2 is unstable and undergoes aerial oxidation to give 4.A similar product(6)from 5 is somehow stabilized by the extra ben- zoyloxy group(or OH)and can be stored without deterioration.
基金The investigation is supported by the WeIding Labc--ratory, Institute of Metal Research of Chinese Atedemy Qf SciEllcGs.
文摘A softening zone with recrystallized grain around the prepared crack tip in the shock waves treated C-Mn steel weld metal was observed. It is suggested that a dynamic recovery occurred around the prepared crack tip even at a low explosion pressure (5 GPa) because of the stress and strain concentration at the crack tip when shock waves pass through. This result supports the previous work on the improved mechanical properties of a shock treated welded joint with residual crack from the viewpoint of microstructure.
文摘The microphase separation extent of biomedical segmented polyetherurethanes were greatly enhanced due to the presence of sulfoalkyl pendant groups contained in the hard segments,and the hard segments were more orderly aggregated through ionic interaction.
文摘The spectral data and chemical properties of two new amides isolated from Clausena lansium led to the assignment of acyclic structures of C-6 and C-7. The absolute configurations of the two chiral carbons in C-6 were determined by degradation to be 3S4R.
文摘2-Acetyl-5-methyl-2H-1,2,3—diaraphosphole 1 reacted with 2—butyne—1, 4—diol to form a tricoordinated phosphorus compound 7, which then rearranged to a novel 2, 3-disubstituted-1, 3-diene.Similar rearrangement has been observed when diphenylchloropbosphine reacted with 2-butyne—1,4-diol
文摘Intramolecular cyclization of A catalyzed by IDA in benzene or THF yields two γ-lactams through C-alkylation and one δ-and one 7-membered lactam by O-alkylation.
文摘When the title compound was treated in protic solvent with alkali catalyses,γ-lacatam was almost the sole product.The ratio of ketone 1 to ketone 2 depended upon the reaction condition.
