PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octa...PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis.展开更多
In this paper,we determine graphs with the largest Laplacian spectral radius among the unicyclic and the bicyclic graphs on n vertices with k pendant vertices,respectively.
The atom-bond connectivity（ABC） index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC（G） =∑ uv∈E（G） √d u＋dv-2 dudv,...The atom-bond connectivity（ABC） index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC（G） =∑ uv∈E（G） √d u＋dv-2 dudv,where du denotes the degree of a vertex u in G.A chemical graph is a graph in which no vertex has degree greater than 4.In this paper,we obtain the sharp upper and lower bounds on ABC index of chemical bicyclic graphs.展开更多
Zhigancao decoction is a traditional prescription for treating irregular pulse and palpitations in China.As the monarch drug of Zhigancao decoction,the bioactive molecules of licorice against heart diseases remain elu...Zhigancao decoction is a traditional prescription for treating irregular pulse and palpitations in China.As the monarch drug of Zhigancao decoction,the bioactive molecules of licorice against heart diseases remain elusive.We established the HRESIMS-guided method leading to the isolation of three novel bicyclic peptides,glycnsisitins A-C(1-3),with distinctive C-C and C-O-C side-chain-toside-chain linkages from the roots of Glycyrrhiza uralensis(Licorice).Glycnsisitin A demonstrated stronger cardioprotective activity than glycnsisitins B and C in an in vitro model of doxorubicin(DOX)-induced cardiomyocyte injury.Glycnsisitin A treatment not only reduced the mortality of heart failure(HF)mice in a dose-dependent manner but also significantly attenuated DOX-induced cardiac dysfunction and myocardial fibrosis.Gene set enrichment analysis(GSEA)of the differentially expressed genes indicated that the cardioprotective effect of glycnsisitin A was mainly attributed to its ability to maintain iron homeostasis in the myocardium.Mechanistically,glycnsisitin A interacted with transferrin and facilitated its binding to the transferrin receptor(TFRC),which caused increased uptake of iron in cardiomyocytes.These findings highlight the key role of bicyclic peptides as bioactive molecules of Zhigancao decoction for the treatment of HF,and glycnsisitin A constitutes a promising therapeutic agent for the treatment of HF.展开更多
The Laplacian spread of a graph is defined to be the difference between the largest eigenvalue and the second smallest eigenvalue of the Laplacian matrix of the graph. In our recent work, we have determined the graphs...The Laplacian spread of a graph is defined to be the difference between the largest eigenvalue and the second smallest eigenvalue of the Laplacian matrix of the graph. In our recent work, we have determined the graphs with maximal Laplacian spreads among all trees of fixed order and among all unicyclic graphs of fixed order, respectively. In this paper, we continue the work on Laplacian spread of graphs, and prove that there exist exactly two bicyclic graphs with maximal Laplacian spread among all bicyclic graphs of fixed order, which are obtained from a star by adding two incident edges and by adding two nonincident edges between the pendant vertices of the star, respectively.展开更多
Ab initio molecular orbital calculations have been performed at Hartree-Fock （HF）, second-order Mrller-Plesset （MP2）, and hybrid density functional theory （DFT） B3LYP levels with 6-31G^＊＊ basis set to investig...Ab initio molecular orbital calculations have been performed at Hartree-Fock （HF）, second-order Mrller-Plesset （MP2）, and hybrid density functional theory （DFT） B3LYP levels with 6-31G^＊＊ basis set to investigate the low sensitive explosive trans-1,4,5,8-tetranitro-1,4,5,8- tetraazadecalin （TNAD） and its seven bicyclic isomers. Their molecular geometries, electronic structures, thermodynamic properties, and detonation performances were predicted and compared. The relationships between structures and various properties were discussed in detail. The calculated results agree well with the available experimental data, and suggest that some compounds may be novel potential candidates of high energy density materials （HEDMs） with performances better than TNT （2,4,6-trinitrotoluene） and similar to RDX （1,3,5-trinitro-1,3,5-triazacyclohexane）.展开更多
Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hes...Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hesigewula Sag were analyzed by gas chromatography-mass spectrometry(GC-MS).C14 bicyclic sesquiterpanes,namely,8β(H)-drimane,8β(H)-homodrimane,and 8 a(H)-homodrimane were detected and identified on basis of their diagnostic fragment ions(m/z123,179,193,and 207),and previously published mass spectra data,and these bicyclic sesquiterpanes presented relatively regular characteristics in their thermal evolution.The ratios 8β(H)-drimane/8β(H)-homodrimane,8β(H)-homodrimane/8 a(H)-homodrimane,and 8β(H)-drimane/8 a(H)-homodrimane all show a clear upward trend with increasing temperature below the temperature turning point.Thus,all these ratios can be used as evolution indexes of source rocks in the immature-lowmaturity stage.However,the last two ratios may be more suitable than the first ratio as valid parameters for measuring the extent of thermal evolution of organic matter in the immature-low-maturity stage because their change amplitude with increasing temperature is more obvious.展开更多
A DFT calculations are carried out at UB3LYP/6-311＋ ＋G （3df, 2p） levels of theory to study electrocyclic thermal cleavage of four （R） derivatives of unsaturated bicyclic diaziridines, Ix-R, to produce correspond...A DFT calculations are carried out at UB3LYP/6-311＋ ＋G （3df, 2p） levels of theory to study electrocyclic thermal cleavage of four （R） derivatives of unsaturated bicyclic diaziridines, Ix-R, to produce corresponding （Z） and （E） azomethine imides （2X-Z, 2X-E, 3X-Z and 3X-E）, where X=H, Me, t-Bu and Ph. Cleavage of 1X-R series to form the most stable 3X-Z product, （path 2） is found the favored procedure because of delocalized negative charge on five atoms and lower steric effect in related transition state. According to IRC calculations in paths 1 and 2, C6--N1 bond is cleaved before the rate determinating step （transition state）. The stability of unsaturated bicyclic diaziridines and their corresponding （Z） and （E） azomethine imides is in the following order in gas phase and chloroform, tetrahydrofuran, and acetone solvents： 3X-Z〈3X-F〈2X-Z 〈2X-E 〈 1X-R 〈 1X-S.展开更多
Three novel bicyclic taxane diterpenoids with the rare 6/12-membered rings wereisolated from the need ies of Taxus chinensis var. mairei. The structures were established with the help of 1D and 2D NMR spectral analysis.
A graph G of order n is called a bicyclic graph if G is connected and the number of edges of G is n＋1. Let B（n） be the set of all bicyclic graphs on n vertices. In this paper, the first three largest spectral radii...A graph G of order n is called a bicyclic graph if G is connected and the number of edges of G is n＋1. Let B（n） be the set of all bicyclic graphs on n vertices. In this paper, the first three largest spectral radii in the class B（n） （n ≥9） together with the corresponding graphs are given.展开更多
A regioselective C-C bond cleavage/aminocarbonylation cascade is presented. In recent years, tremendous progress has been made in the alkoxyl radical-mediated C-C bond cleavage of unstrained monocarbocycles. In contra...A regioselective C-C bond cleavage/aminocarbonylation cascade is presented. In recent years, tremendous progress has been made in the alkoxyl radical-mediated C-C bond cleavage of unstrained monocarbocycles. In contrast, the deconstruction and functionalization of bicyclic skeletons has been less developed and has mainly focused on the ring expansion process. Inspired by the aromatization-driven C-C bond cleavage, here we demonstrate a ring-opening/aminocarbonylation cascade under copper catalysis, in which the formation of a stable γ-lactam or succinimide skeleton reverses the selectivity of C-C cleavage. Remarkably, the photo and thermal assistance is not required when the succinimide skeleton is formed during the ring opening process. DFT calculations revealed that this unexpected ring-opening process is thermodynamically and kinetically favourable.展开更多
A graph has exactly two main eigenvalues if and only if it is a 2-walk linear graph.In this paper,we show some necessary conditions that a 2-walk（a,b）-linear graph must obey.Using these conditions and some basic the...A graph has exactly two main eigenvalues if and only if it is a 2-walk linear graph.In this paper,we show some necessary conditions that a 2-walk（a,b）-linear graph must obey.Using these conditions and some basic theorems in graph theory,we characterize all 2-walk linear graphs with small cyclic graphs without pendants.The results are given in sort on unicyclic,bicyclic,tricyclic graphs.展开更多
The spectral spread of a graph is defined to be the difference between the largest and the least eigenvalue of the adjacency matrix of the graph. A graph G is said to be bicyclic, if G is connected and ｜E（G）｜ = ...The spectral spread of a graph is defined to be the difference between the largest and the least eigenvalue of the adjacency matrix of the graph. A graph G is said to be bicyclic, if G is connected and ｜E（G）｜ = ｜V （G）｜ ＋ 1. Let B（n, g） be the set of bicyclic graphs on n vertices with girth g. In this paper some properties about the least eigenvalues of graphs are given, by which the unique graph with maximal spectral spread in B（n, g） is determined.展开更多
A new bicyclic spiroketone was isolated from the bud of Chrysanthemum indicum L. The chemical structure was elucidated as （1R, 9S, 10S）-10-hydroxyl-8 （2＇, 4＇-diynehexylidene）- 9-isovaleryloxy-2, 7-dioxaspiro [5,...A new bicyclic spiroketone was isolated from the bud of Chrysanthemum indicum L. The chemical structure was elucidated as （1R, 9S, 10S）-10-hydroxyl-8 （2＇, 4＇-diynehexylidene）- 9-isovaleryloxy-2, 7-dioxaspiro [5, 4] decane based on the X-ray crystallography.展开更多
The title compound N-（pyridin-2-ylmethyl）- 1-phenyl- 1,4,5,6,7,8-hexahydrocy-clohepta[c]pyrazole-3-carboxamide 5 （C21I-I22N40, Mr = 346.42） has been synthesized andstructurally characterized by IR, 1H NMR, 13C NMR...The title compound N-（pyridin-2-ylmethyl）- 1-phenyl- 1,4,5,6,7,8-hexahydrocy-clohepta[c]pyrazole-3-carboxamide 5 （C21I-I22N40, Mr = 346.42） has been synthesized andstructurally characterized by IR, 1H NMR, 13C NMR, H RMS and single-crystal X-raydiffraction. The crystal crystallizes in monoclinic system, space group P21/n with a = 8.668（2）,b = 22.236（4）, c = 9.539（2） A, β = 108.68（3）°, V = 1786.4（7）/k3, Z = 4, Dx= 1.288 g/cm3,F（000） = 736,μ（MoKa） = 0.649 mm^-1, the final R = 0.0354 and wR = 0.0933 with 3234observed reflections with I 〉 2σ（/）. The benzene and pyrazole rings are nearly coplanar with adihedral angle of 50.977（46）°. The dihedral angle between the central pyrazole and pyridinerings is 11.688（46）°. No classical hydrogen bonds were found in the molecules. Two adjacentmolecules in crystal packing of compound 5 were linked by two intramolecularhydrogen-bonding interactions C（15）-H（15）…O（1） to generate a stable structure. Compound 5had weak insecticidal activity against the diamondback moth （Plutella xylostella）, butexhibited good activity against cotton bollworm （Helicoverpa armigera）.展开更多
The molecular composition and biomarker distribution of various occurrences of organic matter in argillaceous source rocks developed in fresh and saline lacustrine environments were revealed by successive treatments o...The molecular composition and biomarker distribution of various occurrences of organic matter in argillaceous source rocks developed in fresh and saline lacustrine environments were revealed by successive treatments of solvent extraction followed by acid hydrolysis using gas chromatography–mass spectrometry. The free fraction obtained by solvent extraction provided abundant geochemical information concerning the sedimentary environment, thermal maturity and biogenic origin, and obvious differences existed between fresh and saline lacustrine source rock samples. Our research results indicate that the carbonate-mineral-bound(CM-bound) fraction released by successive acid hydrolysis could also serve as a significant biogenic indicator, as the bicyclic sesquiterpenoids, indicative of Botryococcus braunii origin, were specifically detected in quite high abundance in the acid-soluble fraction. In addition, the light end hydrocarbons were much better preserved in the acid-soluble fraction, and elemental sulfur was only detected in the CM-bound fraction, suggesting a relatively confined environment for the CM-bound fraction, which thus could preserve additional geochemical information compared to that of the free fraction. The CM-bound fraction also exhibited discernable differences between fresh and saline lacustrine samples. Therefore, it can be concluded that comprehensive analysis of free and CM-bound fractions in the argillaceous source rocks can provide a more authentic and objective interpretation of geologic conditions.展开更多
Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-l-pho-sphabicyclo [ 2.2.2 ] octane （PEPA） as starting material. Within them were three PEPA derivatives contain...Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-l-pho-sphabicyclo [ 2.2.2 ] octane （PEPA） as starting material. Within them were three PEPA derivatives containing single caged bicyclic phosphate structure（ 1a, 2a, 3a）, another three PEPA deviratives containing two caged bicyclic phosphate structures（1b, 2b, 3b） and one devirative（1c） containing three caged bicyclic phosphate structures. Structures of the products were characterized by FTIR, ^1H NMR, elemental analysis and TG analysis. The reaction conditions were also discussed. Thermal analysis showed they had high thermal stability and excellent char-forming ability. Besides, these compounds had pentaerythritol bone and flame retardant dements of phosphorus, bromine or nitrogen simultaneously in their molecules, endowed them with good fire retardancy, and made them can be used as intumescent flame retardant.展开更多
A novel synthesis of 2,3-dihydroimidazo[1,2-a]pyridin-5 (1H)-one 4 and its derivatives were described.Preliminary bioassays showed that some of the target compounds exhibited excellent insecticidal activities against ...A novel synthesis of 2,3-dihydroimidazo[1,2-a]pyridin-5 (1H)-one 4 and its derivatives were described.Preliminary bioassays showed that some of the target compounds exhibited excellent insecticidal activities against brown planthopper (Nilaparvata lugens), cowpea aphids (Aphis craccivora) (4,5 a, 5 c, 5 g,5 h, 5 j, 5 r, 6 b, 6 e) and carmine spider mite (Tetranychus cinnabarinus (5 f, 5 s, 6 a) at 500 mg/L. Among them,compound 4 was still active against brown planthopper and cowpea aphids at 4 mg/L. The insecticidal activities were influenced by the types and position of the substituents, which provided guidance for the structure modifications.展开更多
Enantiomerically enriched (R)-1-(2-bromocycloalkenyl)-3-buten-1-ol and its derivatives were obtained via enantioselective hydrolysis [resolution] with good enantioselectivities (E = 31 to >500) using Candida paraps...Enantiomerically enriched (R)-1-(2-bromocycloalkenyl)-3-buten-1-ol and its derivatives were obtained via enantioselective hydrolysis [resolution] with good enantioselectivities (E = 31 to >500) using Candida parapsilosis ATCC 7330. The various reaction parameters were optimized for enantioselective hydrolysis to achieve high enantiomeric excess (ee) and conversions. Among the substrates tested, (RS)-1-(2-bromocyclohex-1-en-1-yl) but-3-yn-1-yl acetate was hydrolysed by the biocatalyst in 12 h to the corresponding (R)-alcohol in 49% conversion and >99 ee. The optically pure allylic alcohol thus obtained was used as a chiral starting material for the synthesis of an enantiomerically enriched bicyclic alcohol effectively establishing achemoenzymatic route.展开更多
文摘PI novel caged bicyclic phosphate flame retardant tri(1-oxo-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane-methyl) phosphate (Trimer) was synthesized from 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo [2.2.2] octane (PEPA) and phosphorus oxychloride in this paper. Its structure was characterized by elemental analysis. FTIR, H-1 NMR. P-31 NMR and X-ray diffraction analysis.
基金supported by National Natural Science Foundation of China (Grant No.10871204)the Fundamental Research Funds for the Central Universities (Grant No.09CX04003A)
文摘In this paper,we determine graphs with the largest Laplacian spectral radius among the unicyclic and the bicyclic graphs on n vertices with k pendant vertices,respectively.
基金Supported by the National Natural Science Foundation of China(11071272,10831001,11171279,11101087)the Young Talent Foundation of Fuzhou University(XRC-1154)
文摘The atom-bond connectivity（ABC） index provides a good model for the stability of linear and branched alkanes as well as the strain energy of cycloalkanes,which is defined as ABC（G） =∑ uv∈E（G） √d u＋dv-2 dudv,where du denotes the degree of a vertex u in G.A chemical graph is a graph in which no vertex has degree greater than 4.In this paper,we obtain the sharp upper and lower bounds on ABC index of chemical bicyclic graphs.
基金supported by Chinese Academy of Medical Sciences(CAMS)Innovation Fund for Medical Sciences(2022-I2M-2-002,2021-I2M-1-016,and 2022-I2M-1-014,China)the Beijing Outstanding Young Scientist Program(BJJWZYJH01201910023028,China)Chinese Academy of Medical Sciences(CAMS)Central Public-interest Scientific Institution Basal Research Fund(2018PT35004,Molecular Mechanism and Target Discovery of Metabolic Disorder and Tumorigenesis,CAMS Key Laboratory).
文摘Zhigancao decoction is a traditional prescription for treating irregular pulse and palpitations in China.As the monarch drug of Zhigancao decoction,the bioactive molecules of licorice against heart diseases remain elusive.We established the HRESIMS-guided method leading to the isolation of three novel bicyclic peptides,glycnsisitins A-C(1-3),with distinctive C-C and C-O-C side-chain-toside-chain linkages from the roots of Glycyrrhiza uralensis(Licorice).Glycnsisitin A demonstrated stronger cardioprotective activity than glycnsisitins B and C in an in vitro model of doxorubicin(DOX)-induced cardiomyocyte injury.Glycnsisitin A treatment not only reduced the mortality of heart failure(HF)mice in a dose-dependent manner but also significantly attenuated DOX-induced cardiac dysfunction and myocardial fibrosis.Gene set enrichment analysis(GSEA)of the differentially expressed genes indicated that the cardioprotective effect of glycnsisitin A was mainly attributed to its ability to maintain iron homeostasis in the myocardium.Mechanistically,glycnsisitin A interacted with transferrin and facilitated its binding to the transferrin receptor(TFRC),which caused increased uptake of iron in cardiomyocytes.These findings highlight the key role of bicyclic peptides as bioactive molecules of Zhigancao decoction for the treatment of HF,and glycnsisitin A constitutes a promising therapeutic agent for the treatment of HF.
基金Supported by the National Natural Science Foundation of China (Grant No.10601001)the Natural Science Foundation of Anhui Province (Grant No.070412065)+3 种基金Project of Anhui Province for Young Teachers Research Supportin Universities (Grant No.2008jql083)Natural Science Foundation of Department of Education of Anhui Province(Grant No.2005kj005zd)Project of Anhui University on Leading Researchers ConstructionFoundation of Innovation Team on Basic Mathematics of Anhui University
文摘The Laplacian spread of a graph is defined to be the difference between the largest eigenvalue and the second smallest eigenvalue of the Laplacian matrix of the graph. In our recent work, we have determined the graphs with maximal Laplacian spreads among all trees of fixed order and among all unicyclic graphs of fixed order, respectively. In this paper, we continue the work on Laplacian spread of graphs, and prove that there exist exactly two bicyclic graphs with maximal Laplacian spread among all bicyclic graphs of fixed order, which are obtained from a star by adding two incident edges and by adding two nonincident edges between the pendant vertices of the star, respectively.
基金The project was supported by NNSFC (Nos. 10576030 and 10576016) and the Innovation Project for Postgraduates in the Universities of Jiangsu Province (AD20116)
文摘Ab initio molecular orbital calculations have been performed at Hartree-Fock （HF）, second-order Mrller-Plesset （MP2）, and hybrid density functional theory （DFT） B3LYP levels with 6-31G^＊＊ basis set to investigate the low sensitive explosive trans-1,4,5,8-tetranitro-1,4,5,8- tetraazadecalin （TNAD） and its seven bicyclic isomers. Their molecular geometries, electronic structures, thermodynamic properties, and detonation performances were predicted and compared. The relationships between structures and various properties were discussed in detail. The calculated results agree well with the available experimental data, and suggest that some compounds may be novel potential candidates of high energy density materials （HEDMs） with performances better than TNT （2,4,6-trinitrotoluene） and similar to RDX （1,3,5-trinitro-1,3,5-triazacyclohexane）.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41672117 and 41503034)the Hubei Provincial Natural Science Foundation of China (Project No. 2017CFA027)+1 种基金the Open Subject of Shandong Provincial Key Laboratory of Depositional Mineralization & Sedimentary Mineral (Baojun Liu Geoscience Science Foundation) (DMSM2017084)the Open Subject of the State Key Laboratory of Petroleum Resources and Prospecting (PRP/open-1509)
文摘Sesquiterpanes are ubiquitous components of crude oils and ancient sediments.Liquid saturated hydrocarbons from simulated pyrolysis experiments on immature organic-rich mudstone collected from the Lower Cretaceous Hesigewula Sag were analyzed by gas chromatography-mass spectrometry(GC-MS).C14 bicyclic sesquiterpanes,namely,8β(H)-drimane,8β(H)-homodrimane,and 8 a(H)-homodrimane were detected and identified on basis of their diagnostic fragment ions(m/z123,179,193,and 207),and previously published mass spectra data,and these bicyclic sesquiterpanes presented relatively regular characteristics in their thermal evolution.The ratios 8β(H)-drimane/8β(H)-homodrimane,8β(H)-homodrimane/8 a(H)-homodrimane,and 8β(H)-drimane/8 a(H)-homodrimane all show a clear upward trend with increasing temperature below the temperature turning point.Thus,all these ratios can be used as evolution indexes of source rocks in the immature-lowmaturity stage.However,the last two ratios may be more suitable than the first ratio as valid parameters for measuring the extent of thermal evolution of organic matter in the immature-low-maturity stage because their change amplitude with increasing temperature is more obvious.
文摘A DFT calculations are carried out at UB3LYP/6-311＋ ＋G （3df, 2p） levels of theory to study electrocyclic thermal cleavage of four （R） derivatives of unsaturated bicyclic diaziridines, Ix-R, to produce corresponding （Z） and （E） azomethine imides （2X-Z, 2X-E, 3X-Z and 3X-E）, where X=H, Me, t-Bu and Ph. Cleavage of 1X-R series to form the most stable 3X-Z product, （path 2） is found the favored procedure because of delocalized negative charge on five atoms and lower steric effect in related transition state. According to IRC calculations in paths 1 and 2, C6--N1 bond is cleaved before the rate determinating step （transition state）. The stability of unsaturated bicyclic diaziridines and their corresponding （Z） and （E） azomethine imides is in the following order in gas phase and chloroform, tetrahydrofuran, and acetone solvents： 3X-Z〈3X-F〈2X-Z 〈2X-E 〈 1X-R 〈 1X-S.
文摘Three novel bicyclic taxane diterpenoids with the rare 6/12-membered rings wereisolated from the need ies of Taxus chinensis var. mairei. The structures were established with the help of 1D and 2D NMR spectral analysis.
基金the National Natural Science Foundation of China(10331020).
文摘A graph G of order n is called a bicyclic graph if G is connected and the number of edges of G is n＋1. Let B（n） be the set of all bicyclic graphs on n vertices. In this paper, the first three largest spectral radii in the class B（n） （n ≥9） together with the corresponding graphs are given.
基金supported by the National Natural Science Foundation of China (Nos. 22171220)the Fundamental Research Funds of the Central Universities (No. xtr072022003)。
文摘A regioselective C-C bond cleavage/aminocarbonylation cascade is presented. In recent years, tremendous progress has been made in the alkoxyl radical-mediated C-C bond cleavage of unstrained monocarbocycles. In contrast, the deconstruction and functionalization of bicyclic skeletons has been less developed and has mainly focused on the ring expansion process. Inspired by the aromatization-driven C-C bond cleavage, here we demonstrate a ring-opening/aminocarbonylation cascade under copper catalysis, in which the formation of a stable γ-lactam or succinimide skeleton reverses the selectivity of C-C cleavage. Remarkably, the photo and thermal assistance is not required when the succinimide skeleton is formed during the ring opening process. DFT calculations revealed that this unexpected ring-opening process is thermodynamically and kinetically favourable.
基金Supported by the National Natural Science Foundation of China (10671081)
文摘A graph has exactly two main eigenvalues if and only if it is a 2-walk linear graph.In this paper,we show some necessary conditions that a 2-walk（a,b）-linear graph must obey.Using these conditions and some basic theorems in graph theory,we characterize all 2-walk linear graphs with small cyclic graphs without pendants.The results are given in sort on unicyclic,bicyclic,tricyclic graphs.
基金Supported by the National Natural Science Foundation of China(No.11101057)China Postdoctoral Science Foundation(No.20110491443)+1 种基金the NSF of Education Ministry of Anhui province(No.KJ2012Z283)Scientific Research Foundation of Chuzhou University(No.2011kj004B)
文摘The spectral spread of a graph is defined to be the difference between the largest and the least eigenvalue of the adjacency matrix of the graph. A graph G is said to be bicyclic, if G is connected and ｜E（G）｜ = ｜V （G）｜ ＋ 1. Let B（n, g） be the set of bicyclic graphs on n vertices with girth g. In this paper some properties about the least eigenvalues of graphs are given, by which the unique graph with maximal spectral spread in B（n, g） is determined.
文摘A new bicyclic spiroketone was isolated from the bud of Chrysanthemum indicum L. The chemical structure was elucidated as （1R, 9S, 10S）-10-hydroxyl-8 （2＇, 4＇-diynehexylidene）- 9-isovaleryloxy-2, 7-dioxaspiro [5, 4] decane based on the X-ray crystallography.
基金financially supported by the National Key Research and Development Plan(No.2017YFD0200504)Hunan Provincial Science and Technology Plan Project(No.2016RS2012)
文摘The title compound N-（pyridin-2-ylmethyl）- 1-phenyl- 1,4,5,6,7,8-hexahydrocy-clohepta[c]pyrazole-3-carboxamide 5 （C21I-I22N40, Mr = 346.42） has been synthesized andstructurally characterized by IR, 1H NMR, 13C NMR, H RMS and single-crystal X-raydiffraction. The crystal crystallizes in monoclinic system, space group P21/n with a = 8.668（2）,b = 22.236（4）, c = 9.539（2） A, β = 108.68（3）°, V = 1786.4（7）/k3, Z = 4, Dx= 1.288 g/cm3,F（000） = 736,μ（MoKa） = 0.649 mm^-1, the final R = 0.0354 and wR = 0.0933 with 3234observed reflections with I 〉 2σ（/）. The benzene and pyrazole rings are nearly coplanar with adihedral angle of 50.977（46）°. The dihedral angle between the central pyrazole and pyridinerings is 11.688（46）°. No classical hydrogen bonds were found in the molecules. Two adjacentmolecules in crystal packing of compound 5 were linked by two intramolecularhydrogen-bonding interactions C（15）-H（15）…O（1） to generate a stable structure. Compound 5had weak insecticidal activity against the diamondback moth （Plutella xylostella）, butexhibited good activity against cotton bollworm （Helicoverpa armigera）.
基金funded by NSFC (National Science Foundation of China) No. 41372130
文摘The molecular composition and biomarker distribution of various occurrences of organic matter in argillaceous source rocks developed in fresh and saline lacustrine environments were revealed by successive treatments of solvent extraction followed by acid hydrolysis using gas chromatography–mass spectrometry. The free fraction obtained by solvent extraction provided abundant geochemical information concerning the sedimentary environment, thermal maturity and biogenic origin, and obvious differences existed between fresh and saline lacustrine source rock samples. Our research results indicate that the carbonate-mineral-bound(CM-bound) fraction released by successive acid hydrolysis could also serve as a significant biogenic indicator, as the bicyclic sesquiterpenoids, indicative of Botryococcus braunii origin, were specifically detected in quite high abundance in the acid-soluble fraction. In addition, the light end hydrocarbons were much better preserved in the acid-soluble fraction, and elemental sulfur was only detected in the CM-bound fraction, suggesting a relatively confined environment for the CM-bound fraction, which thus could preserve additional geochemical information compared to that of the free fraction. The CM-bound fraction also exhibited discernable differences between fresh and saline lacustrine samples. Therefore, it can be concluded that comprehensive analysis of free and CM-bound fractions in the argillaceous source rocks can provide a more authentic and objective interpretation of geologic conditions.
文摘Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethyl-2, 6, 7-trioxa-l-pho-sphabicyclo [ 2.2.2 ] octane （PEPA） as starting material. Within them were three PEPA derivatives containing single caged bicyclic phosphate structure（ 1a, 2a, 3a）, another three PEPA deviratives containing two caged bicyclic phosphate structures（1b, 2b, 3b） and one devirative（1c） containing three caged bicyclic phosphate structures. Structures of the products were characterized by FTIR, ^1H NMR, elemental analysis and TG analysis. The reaction conditions were also discussed. Thermal analysis showed they had high thermal stability and excellent char-forming ability. Besides, these compounds had pentaerythritol bone and flame retardant dements of phosphorus, bromine or nitrogen simultaneously in their molecules, endowed them with good fire retardancy, and made them can be used as intumescent flame retardant.
基金financial supported by the National Key Research Program of China(No. 2017YFD0200500)National Natural Science Foundation of China(No.21672061)supported by the Fundamental Research Funds for the Central Universities(No. 222201718004)
文摘A novel synthesis of 2,3-dihydroimidazo[1,2-a]pyridin-5 (1H)-one 4 and its derivatives were described.Preliminary bioassays showed that some of the target compounds exhibited excellent insecticidal activities against brown planthopper (Nilaparvata lugens), cowpea aphids (Aphis craccivora) (4,5 a, 5 c, 5 g,5 h, 5 j, 5 r, 6 b, 6 e) and carmine spider mite (Tetranychus cinnabarinus (5 f, 5 s, 6 a) at 500 mg/L. Among them,compound 4 was still active against brown planthopper and cowpea aphids at 4 mg/L. The insecticidal activities were influenced by the types and position of the substituents, which provided guidance for the structure modifications.
文摘Enantiomerically enriched (R)-1-(2-bromocycloalkenyl)-3-buten-1-ol and its derivatives were obtained via enantioselective hydrolysis [resolution] with good enantioselectivities (E = 31 to >500) using Candida parapsilosis ATCC 7330. The various reaction parameters were optimized for enantioselective hydrolysis to achieve high enantiomeric excess (ee) and conversions. Among the substrates tested, (RS)-1-(2-bromocyclohex-1-en-1-yl) but-3-yn-1-yl acetate was hydrolysed by the biocatalyst in 12 h to the corresponding (R)-alcohol in 49% conversion and >99 ee. The optically pure allylic alcohol thus obtained was used as a chiral starting material for the synthesis of an enantiomerically enriched bicyclic alcohol effectively establishing achemoenzymatic route.
