Enantioselective domino alkenylation-alkynylation of olefins is achieved for the first time,using terminal alkynes directly as pronucleophiles.The new reaction enables facile construction of azacycles carrying quatern...Enantioselective domino alkenylation-alkynylation of olefins is achieved for the first time,using terminal alkynes directly as pronucleophiles.The new reaction enables facile construction of azacycles carrying quaternary stereocenters,including 5–7 membered pyrrolidines,piperidines and tetrahydroazepines.Moreover,alkynyl groups in azacyclic products provide a useful handle for derivatization that formed both fused and bridged azabicycles.展开更多
We report a density functional theory study on the ruthenium-catalyzed decarbonylative annulation of an alkyne with a six-membered hydroxychromone via C–H/C–C activation.The plausible catalytic cycles involve O–H d...We report a density functional theory study on the ruthenium-catalyzed decarbonylative annulation of an alkyne with a six-membered hydroxychromone via C–H/C–C activation.The plausible catalytic cycles involve O–H deprotonation,C–H activation,alkyne insertion and formal[3+2]cycloaddition,oxidative insertion and decarbonylation,reductive annulation and the recovery of the catalyst.展开更多
Gargantulides B and C,two new and highly complex 52-membered glycosylated macrolactones,were isolated from Amycolatopsis sp.strain CA-230715 during an antibacterial screening campaign.The structures of these giant mac...Gargantulides B and C,two new and highly complex 52-membered glycosylated macrolactones,were isolated from Amycolatopsis sp.strain CA-230715 during an antibacterial screening campaign.The structures of these giant macrolides were elucidated by 2D NMR spectroscopy and shown to be related to gargantulide A,although containing additional β-glucopyranose and/orα-arabinofuranose monosaccharides separately attached to their backbones.Genome sequencing allowed the identification of a strikingly large 216 kbp biosynthetic gene cluster,among the largest type Ⅰ PKS clusters described so far,and the proposal of a previously unreported biosynthetic pathway for gargantulides A-C.The absolute configurations of gargantulides B and C were assigned based on a combination of NMR and bioinformatics analysis of ketoreductase and enoylreductase domains within the multimodular type Ⅰ PKS.In addition,the absolute stereochemistry of gargantulide A has now been revised and completed.Gargantulides B and C display potent antibacterial activity against a set of drug-resistant Gram-positive bacteria and moderate activity against the clinically relevant Gram-negative pathogen Acinetobacter baumannii.展开更多
We report on N,N-bidentate-chelation-assistedα-and β-olefinic C–H alkenylation of aryl alkenes in ethanol to afford aryl dienes/trienes with excellent regio-and stereo-selectivities.The reaction of 2-alkenyl benzyl...We report on N,N-bidentate-chelation-assistedα-and β-olefinic C–H alkenylation of aryl alkenes in ethanol to afford aryl dienes/trienes with excellent regio-and stereo-selectivities.The reaction of 2-alkenyl benzylamine and benzoic acid derived substrates proceeded through six-membered exo-cyclo-metallation and seven-membered endo-cyclometallation.The aerobic protocols feature wide functional-ity tolerance,high selectivities and yields,mild conditions and scalable preparation,and the directing group can be easily removed to afford Boc-protected amine by simple reduction.展开更多
A novel and efficient[3+2]annulation of 2-substituted aziridines and N-tosyl cyanamides via a dominoregioselective ring-opening/5-exo-dig cyclization procedure has been developed,allowing the directpreparation of N_(2...A novel and efficient[3+2]annulation of 2-substituted aziridines and N-tosyl cyanamides via a dominoregioselective ring-opening/5-exo-dig cyclization procedure has been developed,allowing the directpreparation of N_(2)-unprotected five-membered cyclic guanidines in good to excellent yields under mildconditions without metals and strong bases.Moreover,the highly biologically interesting urea analoguescould also be conveniently obtained via hydrolysis of the produced guanidines.展开更多
Cembrene (1), a cembrene-type hydrocarbon diterpene, is the first discovered natural-ly occurring fourteen-membered macrocyclic diterpenoid, which has been found in manyspecies of plant pines. The total synthesis of l...Cembrene (1), a cembrene-type hydrocarbon diterpene, is the first discovered natural-ly occurring fourteen-membered macrocyclic diterpenoid, which has been found in manyspecies of plant pines. The total synthesis of l has been reported by Dauben, Kato展开更多
It has been reported recently that a cyclic dimer adjoining a three-membered ring and a five-membered ring as a repeating unit has been successfully synthesized. It is a planar configuration with a symmetry of D2h and...It has been reported recently that a cyclic dimer adjoining a three-membered ring and a five-membered ring as a repeating unit has been successfully synthesized. It is a planar configuration with a symmetry of D2h and a non-alternated conjugated hydrocarbon with 16 electrons.展开更多
In this paper, a method of local symmetry is applied to metallo-organic 5-membered and 6-membered ring poly-decker sandwiches (briefly called 5-membered sandwich Ⅰ and 6-membered sandwich Ⅱ), and the nature of their...In this paper, a method of local symmetry is applied to metallo-organic 5-membered and 6-membered ring poly-decker sandwiches (briefly called 5-membered sandwich Ⅰ and 6-membered sandwich Ⅱ), and the nature of their chemical bond is discussed by means of the HMO theory. The stable electronic configuration for these sandwiches is obtained. A working rule for the total number of valence electrons being 6(2n+l)+4t is proposed. It is reasonable to suggest some potential synthetic goals of poly-decker sandwiches. The discovery in 1951 of the transition metal π-complex, ferrocene, created a new research field of metalloorganic sandwiches. Since then, a lot of bis-decker sandwich-展开更多
There have been a few theoretical calculations of resonance energies (RE) and bond orders of conjugated hydrocarbons containing a four-membered ring. By using the structure-resonance theory Herndon calculated the RE f...There have been a few theoretical calculations of resonance energies (RE) and bond orders of conjugated hydrocarbons containing a four-membered ring. By using the structure-resonance theory Herndon calculated the RE for a wide range of conjugated hydrocarbons. Although the values calculated for a large number of compounds agree with the best SCF-MO results (the Dewar-de Llano RE), there are wide discrepancies in the case of compounds with a four-membered ring, and the展开更多
In recent years some kinds of iron catalysts for the polymerization of diolefins have been reported. In all of the known iron catalysts, a donor, such as P-com- pound, S-compound, N-compound or O-compound, has to be u...In recent years some kinds of iron catalysts for the polymerization of diolefins have been reported. In all of the known iron catalysts, a donor, such as P-com- pound, S-compound, N-compound or O-compound, has to be used as the third com- ponent besides iron compound and AlR3. Moreover, high catalytic activity occurs only when the third component is a bidentate nitrogen compound which can coordinate with the center iron ion to form a five- or six-membered chelate ring.展开更多
The signals of 1H NMR and 13 C NMR for benzodiheteropine 1 and its cycloaddtion products 2～5 were assigned by two dimensional NMR techniques. The characteristics of their structures were analyzed and ...The signals of 1H NMR and 13 C NMR for benzodiheteropine 1 and its cycloaddtion products 2～5 were assigned by two dimensional NMR techniques. The characteristics of their structures were analyzed and discussed. The boat conformation of the seven membered heteroatomic ring in these structures was interpreted on the basis of the spectrum of NOESY as well. The coupling constants of relative protons were in accord with above results.展开更多
INTRODUCTION Due to their special structures, two nitrogen five-membered heterocyclic com- pounds, including imidazole and pyrazole derivatives, are very important in biochem- istry, medical chemistry, physical chemis...INTRODUCTION Due to their special structures, two nitrogen five-membered heterocyclic com- pounds, including imidazole and pyrazole derivatives, are very important in biochem- istry, medical chemistry, physical chemistry, organic chemistry and catalysis. How- ever, unbranched alkyl-substituted imidazoles and pyrazoles are relatively few.展开更多
Cembrene is a 14-membered carbon ring diterpene compound. Most of its derivatives or isomers possess intensive physiological activity. A series of studies on it have been reported at home and abroad. Recently, a study...Cembrene is a 14-membered carbon ring diterpene compound. Most of its derivatives or isomers possess intensive physiological activity. A series of studies on it have been reported at home and abroad. Recently, a study on its synthesis has been reported展开更多
The basic units of the framework structure of HZSM-5 zeolite are the five-membered rings which are linked by bridging oxygen atoms and as a result form units of four-membered rings or six membered rings. Semiempirical...The basic units of the framework structure of HZSM-5 zeolite are the five-membered rings which are linked by bridging oxygen atoms and as a result form units of four-membered rings or six membered rings. Semiempirical CNDO/2 quantum chemical method is used to calculate the charge density distribution for all these basic units, i.e., 4-, 5- and 6-membered rings of HZSM-5 zeolite. Quantitative relations between the structural parameter α<sub>0</sub> of the acidity of HZSM-5 zeolite and the number of aluminum atoms N<sub>Al</sub> per unit cell are obtained. Zeolite may be considered as solids acting more or less as protonic polyacids in solution. This protonic acidity is expressed as activity, a<sub>H<sup>+</sup></sub>= [H<sup>+</sup>]f<sub>H<sup>+</sup></sub> ,were =n<sub>H<sup>+</sup></sub>aN<sub>Al</sub>/Z<sub>cat</sub> and the activity coefficient f<sub>H<sup>+</sup></sub> is equal to a constant multiplied by the structural parameter, f<sub>H<sup>+</sup></sub>= Kα<sub>0</sub>, K is taken to be 32. Upder different （SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub>） ratios, therefore, the protonic activities could be obtained theoretically, and the calculation results are展开更多
The volatile oil of curcuma, isolated from the root of a turmeric plant, Curcuma aromatica Silisb (a Chinese herbal medicine called wen ezhu), has been proved to be active for treatment of cervix cancer in clinical pr...The volatile oil of curcuma, isolated from the root of a turmeric plant, Curcuma aromatica Silisb (a Chinese herbal medicine called wen ezhu), has been proved to be active for treatment of cervix cancer in clinical practice. The volatile oil consists of several com-展开更多
We report the mass spectrometric investigation on fullerene derivatives C_(60)CH_(2),C_(60)RH,C_(60)R_(2)(R=C_(6)H_(5)CO-)and C_(60)O_(n)under the 308nm laser ablation.In the negative ion mass spectra of C_(60)CH_(2)C...We report the mass spectrometric investigation on fullerene derivatives C_(60)CH_(2),C_(60)RH,C_(60)R_(2)(R=C_(6)H_(5)CO-)and C_(60)O_(n)under the 308nm laser ablation.In the negative ion mass spectra of C_(60)CH_(2)C_(60)R_(2),and C_(60)O_(n),odd-numbered clusters C_(57)^(-),C_(55)^(-),C_(53)^(-),C_(51)^(-)are observed clearly in addition to the even-numbered fullerene fragment ions,while for the monoadduct C60RH,odd-numbered species can not be detected.In the positive ion channel,the fragmentation patterns of the three derivatives are similar.A mechanism related to the structural characteristics of the derivatives is supposed for the odd-numbered duster formation.The 3-membered ring formed on the C_(60)cage is thought of to play a vital role for the formation of odd-numbered carbon clusters.展开更多
Qinghaosu 1 isolated from Artemisia annua L. has attracted great interest in recent years owing to its unique chemical structure and potent antimalarial activity, especially against chloroquine-resistant faleiprum mal...Qinghaosu 1 isolated from Artemisia annua L. has attracted great interest in recent years owing to its unique chemical structure and potent antimalarial activity, especially against chloroquine-resistant faleiprum malaria. A series of studies have been carried out on its reactions, total synthesis and analogs.For preparation of more Qing-展开更多
The active centers of many kinds of iron-sulfur proteins are Fe-S cluster compounds. For example, the active sites of plant ferredoxins, adrenodoxin and putidaredoxin are all Fe2S2 cluster compounds. In addition to Mo...The active centers of many kinds of iron-sulfur proteins are Fe-S cluster compounds. For example, the active sites of plant ferredoxins, adrenodoxin and putidaredoxin are all Fe2S2 cluster compounds. In addition to Mo-Fe-S cluster and Fe4S4 cluster, there is still Fe2S2 cluster in MoFe protein of nitrogenase. Fe-S cluster compounds are展开更多
Squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione) is a four-membered ring oxocarbon compound. The complexes of squaric acid with some divalent and trivalent metals have been investigated. No molybdenum and tungsten...Squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione) is a four-membered ring oxocarbon compound. The complexes of squaric acid with some divalent and trivalent metals have been investigated. No molybdenum and tungsten squarate complexes, however, have been reported. We have found that molybdenum and tungsten squarate complexes can be prepared under selected conditions. Three mmol of sodium tungstate dihydrate in 5 ml of water was mixed with展开更多
Cembrene-C (1), a 14-membered ring diterpene with a special structure, was isolated from some marine sources; 1 has been obtained only in trace amounts through the strong base-catalyzed isomerization of cembrene-A(2)....Cembrene-C (1), a 14-membered ring diterpene with a special structure, was isolated from some marine sources; 1 has been obtained only in trace amounts through the strong base-catalyzed isomerization of cembrene-A(2). Here we report the total synthesis of 1.展开更多
基金supported by the National Natural Science Foundation of China(22271007)the Peking University Shenzhen Graduate School+2 种基金the State Key Laboratory of Chemical Oncogenomicsthe Guangdong Provincial Key Laboratory of Chemical Genomicsthe Shenzhen Bay Laboratory and Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs for JSZ。
文摘Enantioselective domino alkenylation-alkynylation of olefins is achieved for the first time,using terminal alkynes directly as pronucleophiles.The new reaction enables facile construction of azacycles carrying quaternary stereocenters,including 5–7 membered pyrrolidines,piperidines and tetrahydroazepines.Moreover,alkynyl groups in azacyclic products provide a useful handle for derivatization that formed both fused and bridged azabicycles.
基金This work was supported by the National Natural Science Foundation of China(22173010 and 21773010).
文摘We report a density functional theory study on the ruthenium-catalyzed decarbonylative annulation of an alkyne with a six-membered hydroxychromone via C–H/C–C activation.The plausible catalytic cycles involve O–H deprotonation,C–H activation,alkyne insertion and formal[3+2]cycloaddition,oxidative insertion and decarbonylation,reductive annulation and the recovery of the catalyst.
基金funded by grants of the Novo Nordisk Foundation,Denmark[NNF20CC0035580,NNF16OC0021746]Doctoral Programme in Pharmacy(B15.56.1),Doctoral School in Health Sciences,University of Granada,52005 Granada,Spain.
文摘Gargantulides B and C,two new and highly complex 52-membered glycosylated macrolactones,were isolated from Amycolatopsis sp.strain CA-230715 during an antibacterial screening campaign.The structures of these giant macrolides were elucidated by 2D NMR spectroscopy and shown to be related to gargantulide A,although containing additional β-glucopyranose and/orα-arabinofuranose monosaccharides separately attached to their backbones.Genome sequencing allowed the identification of a strikingly large 216 kbp biosynthetic gene cluster,among the largest type Ⅰ PKS clusters described so far,and the proposal of a previously unreported biosynthetic pathway for gargantulides A-C.The absolute configurations of gargantulides B and C were assigned based on a combination of NMR and bioinformatics analysis of ketoreductase and enoylreductase domains within the multimodular type Ⅰ PKS.In addition,the absolute stereochemistry of gargantulide A has now been revised and completed.Gargantulides B and C display potent antibacterial activity against a set of drug-resistant Gram-positive bacteria and moderate activity against the clinically relevant Gram-negative pathogen Acinetobacter baumannii.
基金We gratefully acknowledge the National Natural Science Foundation of China(NSFC)(21672048 and 81570989)Natural Science Foundation of Zhejiang Province(ZJNSF)(LY19B020006)+1 种基金Major Project of Hangzhou Health Science and Technology Plan(Z20200046)Key Subject of Stomatology in Hangzhou for financial support.
文摘We report on N,N-bidentate-chelation-assistedα-and β-olefinic C–H alkenylation of aryl alkenes in ethanol to afford aryl dienes/trienes with excellent regio-and stereo-selectivities.The reaction of 2-alkenyl benzylamine and benzoic acid derived substrates proceeded through six-membered exo-cyclo-metallation and seven-membered endo-cyclometallation.The aerobic protocols feature wide functional-ity tolerance,high selectivities and yields,mild conditions and scalable preparation,and the directing group can be easily removed to afford Boc-protected amine by simple reduction.
基金support from the Natural Science Foundation of Henan Province(grant no.212300410152)the Key Scientific and Technological Project of Henan Province(grant no.212102110439)+1 种基金Henan University of Animal Husbandry and Economy(grant no.2019HNUAHEDF011 and XKYCXJJ2020006)the Key Scientific Research Project for Colleges and Universities of Henan Province(grant no.22B150005)。
文摘A novel and efficient[3+2]annulation of 2-substituted aziridines and N-tosyl cyanamides via a dominoregioselective ring-opening/5-exo-dig cyclization procedure has been developed,allowing the directpreparation of N_(2)-unprotected five-membered cyclic guanidines in good to excellent yields under mildconditions without metals and strong bases.Moreover,the highly biologically interesting urea analoguescould also be conveniently obtained via hydrolysis of the produced guanidines.
基金Project supported by the National Natural Science Foundation of China the Special Research Grant for Doctoral Sites in Universities
文摘Cembrene (1), a cembrene-type hydrocarbon diterpene, is the first discovered natural-ly occurring fourteen-membered macrocyclic diterpenoid, which has been found in manyspecies of plant pines. The total synthesis of l has been reported by Dauben, Kato
文摘It has been reported recently that a cyclic dimer adjoining a three-membered ring and a five-membered ring as a repeating unit has been successfully synthesized. It is a planar configuration with a symmetry of D2h and a non-alternated conjugated hydrocarbon with 16 electrons.
文摘In this paper, a method of local symmetry is applied to metallo-organic 5-membered and 6-membered ring poly-decker sandwiches (briefly called 5-membered sandwich Ⅰ and 6-membered sandwich Ⅱ), and the nature of their chemical bond is discussed by means of the HMO theory. The stable electronic configuration for these sandwiches is obtained. A working rule for the total number of valence electrons being 6(2n+l)+4t is proposed. It is reasonable to suggest some potential synthetic goals of poly-decker sandwiches. The discovery in 1951 of the transition metal π-complex, ferrocene, created a new research field of metalloorganic sandwiches. Since then, a lot of bis-decker sandwich-
文摘There have been a few theoretical calculations of resonance energies (RE) and bond orders of conjugated hydrocarbons containing a four-membered ring. By using the structure-resonance theory Herndon calculated the RE for a wide range of conjugated hydrocarbons. Although the values calculated for a large number of compounds agree with the best SCF-MO results (the Dewar-de Llano RE), there are wide discrepancies in the case of compounds with a four-membered ring, and the
基金Project supported by the National Natural Science Foundation of China
文摘In recent years some kinds of iron catalysts for the polymerization of diolefins have been reported. In all of the known iron catalysts, a donor, such as P-com- pound, S-compound, N-compound or O-compound, has to be used as the third com- ponent besides iron compound and AlR3. Moreover, high catalytic activity occurs only when the third component is a bidentate nitrogen compound which can coordinate with the center iron ion to form a five- or six-membered chelate ring.
文摘The signals of 1H NMR and 13 C NMR for benzodiheteropine 1 and its cycloaddtion products 2～5 were assigned by two dimensional NMR techniques. The characteristics of their structures were analyzed and discussed. The boat conformation of the seven membered heteroatomic ring in these structures was interpreted on the basis of the spectrum of NOESY as well. The coupling constants of relative protons were in accord with above results.
文摘INTRODUCTION Due to their special structures, two nitrogen five-membered heterocyclic com- pounds, including imidazole and pyrazole derivatives, are very important in biochem- istry, medical chemistry, physical chemistry, organic chemistry and catalysis. How- ever, unbranched alkyl-substituted imidazoles and pyrazoles are relatively few.
文摘Cembrene is a 14-membered carbon ring diterpene compound. Most of its derivatives or isomers possess intensive physiological activity. A series of studies on it have been reported at home and abroad. Recently, a study on its synthesis has been reported
文摘The basic units of the framework structure of HZSM-5 zeolite are the five-membered rings which are linked by bridging oxygen atoms and as a result form units of four-membered rings or six membered rings. Semiempirical CNDO/2 quantum chemical method is used to calculate the charge density distribution for all these basic units, i.e., 4-, 5- and 6-membered rings of HZSM-5 zeolite. Quantitative relations between the structural parameter α<sub>0</sub> of the acidity of HZSM-5 zeolite and the number of aluminum atoms N<sub>Al</sub> per unit cell are obtained. Zeolite may be considered as solids acting more or less as protonic polyacids in solution. This protonic acidity is expressed as activity, a<sub>H<sup>+</sup></sub>= [H<sup>+</sup>]f<sub>H<sup>+</sup></sub> ,were =n<sub>H<sup>+</sup></sub>aN<sub>Al</sub>/Z<sub>cat</sub> and the activity coefficient f<sub>H<sup>+</sup></sub> is equal to a constant multiplied by the structural parameter, f<sub>H<sup>+</sup></sub>= Kα<sub>0</sub>, K is taken to be 32. Upder different （SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub>） ratios, therefore, the protonic activities could be obtained theoretically, and the calculation results are
文摘The volatile oil of curcuma, isolated from the root of a turmeric plant, Curcuma aromatica Silisb (a Chinese herbal medicine called wen ezhu), has been proved to be active for treatment of cervix cancer in clinical practice. The volatile oil consists of several com-
基金Supported by the National Natural Science Foundation of China under Grant Nos.29890216 and 69608003,Shanghai Research Center for Applied Physics.
文摘We report the mass spectrometric investigation on fullerene derivatives C_(60)CH_(2),C_(60)RH,C_(60)R_(2)(R=C_(6)H_(5)CO-)and C_(60)O_(n)under the 308nm laser ablation.In the negative ion mass spectra of C_(60)CH_(2)C_(60)R_(2),and C_(60)O_(n),odd-numbered clusters C_(57)^(-),C_(55)^(-),C_(53)^(-),C_(51)^(-)are observed clearly in addition to the even-numbered fullerene fragment ions,while for the monoadduct C60RH,odd-numbered species can not be detected.In the positive ion channel,the fragmentation patterns of the three derivatives are similar.A mechanism related to the structural characteristics of the derivatives is supposed for the odd-numbered duster formation.The 3-membered ring formed on the C_(60)cage is thought of to play a vital role for the formation of odd-numbered carbon clusters.
文摘Qinghaosu 1 isolated from Artemisia annua L. has attracted great interest in recent years owing to its unique chemical structure and potent antimalarial activity, especially against chloroquine-resistant faleiprum malaria. A series of studies have been carried out on its reactions, total synthesis and analogs.For preparation of more Qing-
文摘The active centers of many kinds of iron-sulfur proteins are Fe-S cluster compounds. For example, the active sites of plant ferredoxins, adrenodoxin and putidaredoxin are all Fe2S2 cluster compounds. In addition to Mo-Fe-S cluster and Fe4S4 cluster, there is still Fe2S2 cluster in MoFe protein of nitrogenase. Fe-S cluster compounds are
文摘Squaric acid (3,4-dihydroxy-3-cyclobutene-1,2-dione) is a four-membered ring oxocarbon compound. The complexes of squaric acid with some divalent and trivalent metals have been investigated. No molybdenum and tungsten squarate complexes, however, have been reported. We have found that molybdenum and tungsten squarate complexes can be prepared under selected conditions. Three mmol of sodium tungstate dihydrate in 5 ml of water was mixed with
基金Project supported by the National Natural Science Foundation of China.
文摘Cembrene-C (1), a 14-membered ring diterpene with a special structure, was isolated from some marine sources; 1 has been obtained only in trace amounts through the strong base-catalyzed isomerization of cembrene-A(2). Here we report the total synthesis of 1.
