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1997 Volume 8 Issue 10
1997, 8(10): 841-842
Abstract:
A new method for the cleavage of carbohydrate benzylidene acetal has been developed using Ceric (Ⅳ) ammonium nitrate (CAN) [(NH4)2Ce(NO3)6] in CH3CN-H2O (10/1,v/v).
A new method for the cleavage of carbohydrate benzylidene acetal has been developed using Ceric (Ⅳ) ammonium nitrate (CAN) [(NH4)2Ce(NO3)6] in CH3CN-H2O (10/1,v/v).
1997, 8(10): 843-844
Abstract:
An efficient one-step methyl esterification of carboxylic acid and deacetylation of alcohol under BF3·OEt2-MeOH was developed.
An efficient one-step methyl esterification of carboxylic acid and deacetylation of alcohol under BF3·OEt2-MeOH was developed.
1997, 8(10): 845-846
Abstract:
Three N,N'-heterylmethyl derivates of diaza-18-crown-6(I) are readily prepared by the reaction of (I) with paraformaldehyde and heterocyclic compounds in dry benzene.
Three N,N'-heterylmethyl derivates of diaza-18-crown-6(I) are readily prepared by the reaction of (I) with paraformaldehyde and heterocyclic compounds in dry benzene.
1997, 8(10): 847-848
Abstract:
10β-OH can be acylated cleanly when 7α-OH is also free,and thus a facile access to semi-synthesis of 7-epi-paclitaxel was proposed.A 2's,3's-oxazoline paclitaxel analog was serendipitously synthesized.
10β-OH can be acylated cleanly when 7α-OH is also free,and thus a facile access to semi-synthesis of 7-epi-paclitaxel was proposed.A 2's,3's-oxazoline paclitaxel analog was serendipitously synthesized.
1997, 8(10): 849-852
Abstract:
A series of dibenzo-sulfur-heterocycle compounds,such as phenothiazine,phenoxthine,thianthrene,thioxanthene and derivatives of dibenzothiophene were synthesized with satisfactory yields through reaction of the corresponding diphenyl-type compounds with elemental sulfur over a USY zeolite catalyst.
A series of dibenzo-sulfur-heterocycle compounds,such as phenothiazine,phenoxthine,thianthrene,thioxanthene and derivatives of dibenzothiophene were synthesized with satisfactory yields through reaction of the corresponding diphenyl-type compounds with elemental sulfur over a USY zeolite catalyst.
1997, 8(10): 853-854
Abstract:
Five new chiral sulfur-containing macrocyclic ligands which can be used in chiral recognition to guests have been synthesized and characterized.
Five new chiral sulfur-containing macrocyclic ligands which can be used in chiral recognition to guests have been synthesized and characterized.
1997, 8(10): 855-858
Abstract:
The stereoselective synthesis of 2-chloro-4-substituted-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinan-2-(thi) ones is described.Only single trans-isomers were obtained when 1-substituted-phenyl-2,2-dimethyl-1,3-propanediols (1) reacted with POCl3.But the stereoselectivity of cyclization reaction between (1) and PSCl3 depended greatly upon the reaction condition.The configurational assignments and the ratio of cis-/trans-diastereoisomers of the products were performed on the basis of 1HNMR,31PNMR and IR spectra and confirmed by X-ray diffraction analyses.
The stereoselective synthesis of 2-chloro-4-substituted-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinan-2-(thi) ones is described.Only single trans-isomers were obtained when 1-substituted-phenyl-2,2-dimethyl-1,3-propanediols (1) reacted with POCl3.But the stereoselectivity of cyclization reaction between (1) and PSCl3 depended greatly upon the reaction condition.The configurational assignments and the ratio of cis-/trans-diastereoisomers of the products were performed on the basis of 1HNMR,31PNMR and IR spectra and confirmed by X-ray diffraction analyses.
1997, 8(10): 859-860
Abstract:
Synthesis of 11-demethyl and 6,6,11-demethyl calanolides A (6-9) have been carried out by a four-step reaction sequence using a simple approach in order to investigate the structural requirements necessary for antiviral activity.
Synthesis of 11-demethyl and 6,6,11-demethyl calanolides A (6-9) have been carried out by a four-step reaction sequence using a simple approach in order to investigate the structural requirements necessary for antiviral activity.
1997, 8(10): 861-862
Abstract:
A precursor 9 of preverecynarmin was prepared by starting from isoprene and geraniol.The key steps in synthesis are the addition of sulfurstabilized carbanion to aldehyde and alkylation with allylic chloride.
A precursor 9 of preverecynarmin was prepared by starting from isoprene and geraniol.The key steps in synthesis are the addition of sulfurstabilized carbanion to aldehyde and alkylation with allylic chloride.
1997, 8(10): 863-864
Abstract:
7-Epi-howiinol A,an antitumor lactone,has been synthesized in nine steps starting from α-D-glucoheptonic γ-lactone with an overall yield of 8.5%.
7-Epi-howiinol A,an antitumor lactone,has been synthesized in nine steps starting from α-D-glucoheptonic γ-lactone with an overall yield of 8.5%.
1997, 8(10): 865-868
Abstract:
α-Chamigrene (12) and β-chamigrene (15) were synthesized via a useful synthon in the synthesis of chamigrene-type sesquiterpenes,i.e.,1-methoxycarbonyl 5,5,9-trimethyl spiro-[5,5] undeca-1,8-dien-3-one(6),which had been prepared from a retro-aldol rearrangement product of proto-[2+2] photocycloadducts obtained by means of photoaddition reaction of terpinolene with methyl 2,4-dioxopentanoate.
α-Chamigrene (12) and β-chamigrene (15) were synthesized via a useful synthon in the synthesis of chamigrene-type sesquiterpenes,i.e.,1-methoxycarbonyl 5,5,9-trimethyl spiro-[5,5] undeca-1,8-dien-3-one(6),which had been prepared from a retro-aldol rearrangement product of proto-[2+2] photocycloadducts obtained by means of photoaddition reaction of terpinolene with methyl 2,4-dioxopentanoate.
1997, 8(10): 869-872
Abstract:
The contact charge transfer (CCT) absorption spectra of isopropyl ether,phenyl isopropyl ether and benzyl isopropyl ether with oxygen were measured.The mechanism of the initial dark oxidation of different ethers via ether-O2 CCT was proposed.
The contact charge transfer (CCT) absorption spectra of isopropyl ether,phenyl isopropyl ether and benzyl isopropyl ether with oxygen were measured.The mechanism of the initial dark oxidation of different ethers via ether-O2 CCT was proposed.
1997, 8(10): 873-874
Abstract:
Ceratoside A (1),a new compound was isolated from the butanol-soluble fraction of Ceratostigma willmottianum,Its structure was determined by the utilization of 2D-NMR techniques.
Ceratoside A (1),a new compound was isolated from the butanol-soluble fraction of Ceratostigma willmottianum,Its structure was determined by the utilization of 2D-NMR techniques.
1997, 8(10): 875-878
Abstract:
A highly sensitive HPLC method for the detection of amino acids and oligopeptides with 9-acridine formyl chloride by.pre-column fluorescence derivatization has been developed.Glycine.glycylglycine,histidine,triglycine and glutathione were separated on a reversed-phase C18 column with methanol-water-triethylamine eluent,derivatization and chromatographic conditions were optimized.The five derivatives were eluted in 28 min with a good reproducibility.Linear range of the calibration graph was 0.08-260 nmol/ml-1.The relative standard deviations(n=6) are < 5%.Detection limits (signal-to-noise ratio=3) for the five derivatives are 20-40 fmol.
A highly sensitive HPLC method for the detection of amino acids and oligopeptides with 9-acridine formyl chloride by.pre-column fluorescence derivatization has been developed.Glycine.glycylglycine,histidine,triglycine and glutathione were separated on a reversed-phase C18 column with methanol-water-triethylamine eluent,derivatization and chromatographic conditions were optimized.The five derivatives were eluted in 28 min with a good reproducibility.Linear range of the calibration graph was 0.08-260 nmol/ml-1.The relative standard deviations(n=6) are < 5%.Detection limits (signal-to-noise ratio=3) for the five derivatives are 20-40 fmol.
1997, 8(10): 879-882
Abstract:
In positive-ion fast atom bombardment (FAB) mass spectrometry,when mono-and di-saccharides are mixed with an appropriate amount of NH4Cl,a highly abundant peak [M+NH4]+ appears in FAB mass spectra.From the adduct ion [M+NH4]+,the molecular weights of mono-and di-saccharides can be determined definitively.
In positive-ion fast atom bombardment (FAB) mass spectrometry,when mono-and di-saccharides are mixed with an appropriate amount of NH4Cl,a highly abundant peak [M+NH4]+ appears in FAB mass spectra.From the adduct ion [M+NH4]+,the molecular weights of mono-and di-saccharides can be determined definitively.
1997, 8(10): 883-884
Abstract:
Fourteen substituted α-phenylcinnamic acids were prepared by the classical Perkin condensation.A plausible way of cleavage was involved in the formation of the specific fragment peaks in the MS of the α-phenylcinnamic acids.The characteristic chemical shift of the olefinic proton in 1HNMR is also discussed.
Fourteen substituted α-phenylcinnamic acids were prepared by the classical Perkin condensation.A plausible way of cleavage was involved in the formation of the specific fragment peaks in the MS of the α-phenylcinnamic acids.The characteristic chemical shift of the olefinic proton in 1HNMR is also discussed.
1997, 8(10): 885-888
Abstract:
A series of trans-4,5-disubstituted-γ-butyrolactones are found to assume two different envelope conformations by means of nuclear magnetic resonance spectroscopy.
A series of trans-4,5-disubstituted-γ-butyrolactones are found to assume two different envelope conformations by means of nuclear magnetic resonance spectroscopy.
1997, 8(10): 889-892
Abstract:
The quantitative structural parameters and activity relationship of pyrrolobenzo-thiazepin-ones and pyrrolobenzoxazepinones' inhibitory activities on HTV-1 reverse transcriptase (RT) was studied.A good relationship has been built.
The quantitative structural parameters and activity relationship of pyrrolobenzo-thiazepin-ones and pyrrolobenzoxazepinones' inhibitory activities on HTV-1 reverse transcriptase (RT) was studied.A good relationship has been built.
1997, 8(10): 893-896
Abstract:
A series of 94 taxol analogues exhibiting antitumor activity were investigated using comparative molecular field analysis (CoMFA) method.The most optimal CoMFA from 80 compounds selected randomly yielded a two-components model,with significant cross-validation r2cv of 0.640 and conventional r2 of 0.868.The robustness of the CoMFA model was further validated by prediction of 14 test set compounds.The CoMFA model explained present SAR and particularly the importance of the hydroxyl group at C-2' position and the stereochemistry at C-2' and C-3' positions.
A series of 94 taxol analogues exhibiting antitumor activity were investigated using comparative molecular field analysis (CoMFA) method.The most optimal CoMFA from 80 compounds selected randomly yielded a two-components model,with significant cross-validation r2cv of 0.640 and conventional r2 of 0.868.The robustness of the CoMFA model was further validated by prediction of 14 test set compounds.The CoMFA model explained present SAR and particularly the importance of the hydroxyl group at C-2' position and the stereochemistry at C-2' and C-3' positions.
1997, 8(10): 897-900
Abstract:
The diffusion coefficients(Dapp) and the heterogeneous electron-transfer rate constants(ks) for ferrocene in MPEG/salt electrolytes were determined by using steady-state voltammetry.The temperature dependence of the two parameters obeys the Arrhenius equation.The effect of the ionic size of six supporting electrolytes on diffusion and electron transfer dynamics of ferrocene was discussed.
The diffusion coefficients(Dapp) and the heterogeneous electron-transfer rate constants(ks) for ferrocene in MPEG/salt electrolytes were determined by using steady-state voltammetry.The temperature dependence of the two parameters obeys the Arrhenius equation.The effect of the ionic size of six supporting electrolytes on diffusion and electron transfer dynamics of ferrocene was discussed.
1997, 8(10): 901-904
Abstract:
The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks) for ferrocene in several polymer solvents were determined by using steady-state voltammetry.The temperature dependence of the two parameters indicates Arrhenius behavior.The polymer solvent effects on diffusion and electron transfer dynamics of ferrocene were discussed.
The diffusion coefficients(Dapp) and the heterogeneous electron transfer rate constants(ks) for ferrocene in several polymer solvents were determined by using steady-state voltammetry.The temperature dependence of the two parameters indicates Arrhenius behavior.The polymer solvent effects on diffusion and electron transfer dynamics of ferrocene were discussed.
1997, 8(10): 905-908
Abstract:
The electrochemistry of (TPP)Co in the presence of pyridine was investigated in dichloroethane solution by cyclic voltammetry.With the addition of pyridine to the solution,the reduction peaks of the axial complex compounds, (TPP)Co(Ⅲ)(Py) and (TPP)Co(Ⅲ)(Py)2 were observed.It was found that the reduction peak of Co(Ⅱ)/Co(Ⅰ) shifted to about-1.20V (SCE) with the increase of added pyridine.The new reduction peak may be attributed to the direct reduction of the axially complex (TPP)Co(Ⅱ)(Py).
The electrochemistry of (TPP)Co in the presence of pyridine was investigated in dichloroethane solution by cyclic voltammetry.With the addition of pyridine to the solution,the reduction peaks of the axial complex compounds, (TPP)Co(Ⅲ)(Py) and (TPP)Co(Ⅲ)(Py)2 were observed.It was found that the reduction peak of Co(Ⅱ)/Co(Ⅰ) shifted to about-1.20V (SCE) with the increase of added pyridine.The new reduction peak may be attributed to the direct reduction of the axially complex (TPP)Co(Ⅱ)(Py).
1997, 8(10): 909-912
Abstract:
The mixed-valence heteropolyanion VMo12O40n- (where n=4,5,6) in aprotic media was investigated by cyclic voltammetry and in-situ FTIR and UV-visible-near-IR spectroelectrochemical methods.The results indicate that the heteropolyanion VMo12O403- undergoes three reversible one electron transfer reductions and the mixed-valence heteropolyanion VMo12O40n- (where n=4,5,6) was formed after electroreduction.The spectra of the aforementioned mixed-valence compounds were characterized by in-situ spectroelectrochemical methods.
The mixed-valence heteropolyanion VMo12O40n- (where n=4,5,6) in aprotic media was investigated by cyclic voltammetry and in-situ FTIR and UV-visible-near-IR spectroelectrochemical methods.The results indicate that the heteropolyanion VMo12O403- undergoes three reversible one electron transfer reductions and the mixed-valence heteropolyanion VMo12O40n- (where n=4,5,6) was formed after electroreduction.The spectra of the aforementioned mixed-valence compounds were characterized by in-situ spectroelectrochemical methods.
1997, 8(10): 913-916
Abstract:
A novel multilayer film electrode containing 12-tungstosilicate anions was achieved on the surface of gold electrode by alternating deposition of 12-tungstosilicate anions with 60% quaternized poly(4-vinylpyridine) based on electrostatic interaction.The chemically-modified electrode exhibits a high catalytic activity towards the electroreduction of molecular oxygen.
A novel multilayer film electrode containing 12-tungstosilicate anions was achieved on the surface of gold electrode by alternating deposition of 12-tungstosilicate anions with 60% quaternized poly(4-vinylpyridine) based on electrostatic interaction.The chemically-modified electrode exhibits a high catalytic activity towards the electroreduction of molecular oxygen.
1997, 8(10): 917-918
Abstract:
Single crystals of MDA [Ni(dmit)2]2 were synthesized by using electrooxidation method.Electrical conductivity measurements exhibit a semiconducting feature with high conductivity at room temperature.
Single crystals of MDA [Ni(dmit)2]2 were synthesized by using electrooxidation method.Electrical conductivity measurements exhibit a semiconducting feature with high conductivity at room temperature.
1997, 8(10): 919-922
Abstract:
LaC2+,LaC22+,LaC3 and LaC3- clusters have been studied using B3LYP density functional method.Four isomers with C2V,CS,C∞V and D∞h symmetry were presented for LaC2+ and LaC22+.Meanwhile,two spin states,namely,singlet and triplet for LaC2+,doublet and quartet for LaC22+,were considered.The results indicated that ring isomers with C2V and CS symmetry are the most stable for LaC2+ at both spin states and for LaC22+ at quartet state.Whereas for LaC22+ at doublet state,linear isomer with C∞V symmetry is energetically favored.For LaC3 and LaC3- clusters,three isomers have been presented for each cluster,that is,two ring isomers with C2V symmetry (in one of them,La forms two single bonds with two carbons,and in another,La forms a double bond with carbon),and one linear isomer with C∞V symmetry.The results revealed that the ring isomer in which La forms two single bonds with carbons is the lowest in energy.
LaC2+,LaC22+,LaC3 and LaC3- clusters have been studied using B3LYP density functional method.Four isomers with C2V,CS,C∞V and D∞h symmetry were presented for LaC2+ and LaC22+.Meanwhile,two spin states,namely,singlet and triplet for LaC2+,doublet and quartet for LaC22+,were considered.The results indicated that ring isomers with C2V and CS symmetry are the most stable for LaC2+ at both spin states and for LaC22+ at quartet state.Whereas for LaC22+ at doublet state,linear isomer with C∞V symmetry is energetically favored.For LaC3 and LaC3- clusters,three isomers have been presented for each cluster,that is,two ring isomers with C2V symmetry (in one of them,La forms two single bonds with two carbons,and in another,La forms a double bond with carbon),and one linear isomer with C∞V symmetry.The results revealed that the ring isomer in which La forms two single bonds with carbons is the lowest in energy.
1997, 8(10): 923-926
Abstract:
Based on four constant parameters (the site energy differences EM2-EM1=25.50 kJ/mol,EM3-EM1=-10.73 kJ/mol and the potential energies of interactions between the cation pairs occupying adjacent sites W12=45.60 kJ/mol,W14=0.56 kJ/mol) and a temperature-dependent parameter EM4-EM1=2.68 (T/7323)2.5 kJ/mol,the equilibrium distributions of the exchangeable cations,K+,s,over those four available cation sites in K22.4Al22.4Si73.6O192 are studied by the simulated annealing method.
Based on four constant parameters (the site energy differences EM2-EM1=25.50 kJ/mol,EM3-EM1=-10.73 kJ/mol and the potential energies of interactions between the cation pairs occupying adjacent sites W12=45.60 kJ/mol,W14=0.56 kJ/mol) and a temperature-dependent parameter EM4-EM1=2.68 (T/7323)2.5 kJ/mol,the equilibrium distributions of the exchangeable cations,K+,s,over those four available cation sites in K22.4Al22.4Si73.6O192 are studied by the simulated annealing method.
1997, 8(10): 927-930
Abstract:
A novel aluminosilicate with well-defined bimodal mesopore distribution has been synthesized directly,in which one mesopore is distributed at around 3.8nm and the other at 2.6nm.
A novel aluminosilicate with well-defined bimodal mesopore distribution has been synthesized directly,in which one mesopore is distributed at around 3.8nm and the other at 2.6nm.
1997, 8(10): 931-934
Abstract:
The feasibility of preparing high Si/Al ratio samples by treating USY zeolites with citric acid solution in unbuffered system was extensively investigated.The effect of treating conditions was explored.The results show that Si/Al ratios,crystallinities,contents of crystalline silicon and thermal stabilities of the samples are greatly increased after moderate modification.It means that it might be an effective method for the moderate modification of USY samples.
The feasibility of preparing high Si/Al ratio samples by treating USY zeolites with citric acid solution in unbuffered system was extensively investigated.The effect of treating conditions was explored.The results show that Si/Al ratios,crystallinities,contents of crystalline silicon and thermal stabilities of the samples are greatly increased after moderate modification.It means that it might be an effective method for the moderate modification of USY samples.
