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1998 Volume 9 Issue 4
1998, 9(4): 321-323
Abstract:
The photoinduced intramolecular meta-cycloaddition of bichromophores 1a-1d gave diastereoselectively two types of adducts 2a-2d and 3a-3d respectively. The observed stereochemistry of cycloaddition is rationalized in terms of hydrogen bond effect induced by the 4-hydroxy group in the 5-phenylpent-1-ene skeleton.
The photoinduced intramolecular meta-cycloaddition of bichromophores 1a-1d gave diastereoselectively two types of adducts 2a-2d and 3a-3d respectively. The observed stereochemistry of cycloaddition is rationalized in terms of hydrogen bond effect induced by the 4-hydroxy group in the 5-phenylpent-1-ene skeleton.
1998, 9(4): 325-328
Abstract:
The studies on the asymmetric alkylation of ester employing D-Isomannide and D-isosorbide as chiral auxiliaries were described. The diastereomeric excess of this reaction was up to 90%.
The studies on the asymmetric alkylation of ester employing D-Isomannide and D-isosorbide as chiral auxiliaries were described. The diastereomeric excess of this reaction was up to 90%.
1998, 9(4): 329-332
Abstract:
Three asymmetrically substituted cyclohexanes were prepared from one-pot reactions of aldehydes and methylketones, and the products were characterized by single crystal structure analysis, NMR spectroscopy and microanalysis.
Three asymmetrically substituted cyclohexanes were prepared from one-pot reactions of aldehydes and methylketones, and the products were characterized by single crystal structure analysis, NMR spectroscopy and microanalysis.
1998, 9(4): 333-334
Abstract:
The cleavage activity of histidyl-lysine dipeptide (His-Lys) on RNA was studied and compared with that of histidine. With the addition of the lysine residue, the cleavage activity was increased about 10-fold compared to that of histidine. The cleavage mechanism of His-Lys was also discussed.
The cleavage activity of histidyl-lysine dipeptide (His-Lys) on RNA was studied and compared with that of histidine. With the addition of the lysine residue, the cleavage activity was increased about 10-fold compared to that of histidine. The cleavage mechanism of His-Lys was also discussed.
1998, 9(4): 335-337
Abstract:
A series of chiral lipophilic Cu(Ⅱ) complexes were investigated as catalysts for the enantioselective hydrolysis of R(S)-p-nitrophenyl N-dodecanoyl-phenylalaninate in micelles. The highest enantioselectivity (kR/kS=7.81) was observed in a mixed micellar system composed of 1-Cu(Ⅱ) and Brij35.
A series of chiral lipophilic Cu(Ⅱ) complexes were investigated as catalysts for the enantioselective hydrolysis of R(S)-p-nitrophenyl N-dodecanoyl-phenylalaninate in micelles. The highest enantioselectivity (kR/kS=7.81) was observed in a mixed micellar system composed of 1-Cu(Ⅱ) and Brij35.
1998, 9(4): 339-340
Abstract:
Butyllithium was directly added to the solution of polysaccharides in dimethyl sulfoxide. The methylsulfinyl carbanion, as a sugar alkoxide forming reagent, was generated from the solution. All the operations were performed as one-pot reactions. Five polysaccharides from different traditional Chinese medicines and three dextrans were methylated and satisfactory results have been achieved.
Butyllithium was directly added to the solution of polysaccharides in dimethyl sulfoxide. The methylsulfinyl carbanion, as a sugar alkoxide forming reagent, was generated from the solution. All the operations were performed as one-pot reactions. Five polysaccharides from different traditional Chinese medicines and three dextrans were methylated and satisfactory results have been achieved.
1998, 9(4): 341-343
Abstract:
Ten new bisazo pigments were synthesized by coupling 1,5-diaminoanthraquinone with various couplers. The absorption studies show that a red shift of 50 nm is obtained when the coupler component is changed.
Ten new bisazo pigments were synthesized by coupling 1,5-diaminoanthraquinone with various couplers. The absorption studies show that a red shift of 50 nm is obtained when the coupler component is changed.
1998, 9(4): 345-346
Abstract:
Diethyl malonate was synthesized by transition-metal catalyzed alkoxycarbonylation of ethyl chloroacetate. The results show that the conversion of ethyl chloroacetate is greater than 92%, and the selectivity to diethyl malonate is 67.5%.
Diethyl malonate was synthesized by transition-metal catalyzed alkoxycarbonylation of ethyl chloroacetate. The results show that the conversion of ethyl chloroacetate is greater than 92%, and the selectivity to diethyl malonate is 67.5%.
1998, 9(4): 347-349
Abstract:
Three 3,3"-biflavones were synthesized by using iodination of flavones through I2-CAN system as the key step followed by the coupling of 3-iodoflavones under the Ullmann reaction conditions.
Three 3,3"-biflavones were synthesized by using iodination of flavones through I2-CAN system as the key step followed by the coupling of 3-iodoflavones under the Ullmann reaction conditions.
1998, 9(4): 351-352
Abstract:
Four 8,8"-biflavones were synthesized by the iodination of 2'-hydroxychalcones at 8- position in I2-H2SO4-DMS0 system as the key step followed by coupling under Ullmann reaction conditions.
Four 8,8"-biflavones were synthesized by the iodination of 2'-hydroxychalcones at 8- position in I2-H2SO4-DMS0 system as the key step followed by coupling under Ullmann reaction conditions.
1998, 9(4): 353-356
Abstract:
Stereoselective total synthesis of (±)hinesol 1 was achieved from readily available starting materials and thorough mild reaction conditions. The structure of synthetic hinesol was confirmed by chemical transformation.
Stereoselective total synthesis of (±)hinesol 1 was achieved from readily available starting materials and thorough mild reaction conditions. The structure of synthetic hinesol was confirmed by chemical transformation.
1998, 9(4): 357-360
Abstract:
(±)Chrysotricine 1 was synthesized by a facile route. The key steps in the synthesis were aldol condensation of dilithium salt of harman 4 with 6-methyl-5-hepten-2-one 5 and cyclization of compound 6 using MCPBA. The 1HNMR spectrum of synthetic product was identical to that of the natural sample.
(±)Chrysotricine 1 was synthesized by a facile route. The key steps in the synthesis were aldol condensation of dilithium salt of harman 4 with 6-methyl-5-hepten-2-one 5 and cyclization of compound 6 using MCPBA. The 1HNMR spectrum of synthetic product was identical to that of the natural sample.
1998, 9(4): 361-363
Abstract:
Yakuchinone-A, a natural strong pungent flavor isolated from Alpina oxyphylla, was synthesized starting from vanillin and cinnamaldehyde in five steps and in 62% overall yield.
Yakuchinone-A, a natural strong pungent flavor isolated from Alpina oxyphylla, was synthesized starting from vanillin and cinnamaldehyde in five steps and in 62% overall yield.
1998, 9(4): 365-367
Abstract:
Stereocontrolled synthesis of 3(R) and 3(S)-hydroxyeicos-4(E)-en-1-yne has been achieved through double elimination of chloride intermediates 8 and 11,which were prepared from acetylenic alcohol intermediates 1 and 10.
Stereocontrolled synthesis of 3(R) and 3(S)-hydroxyeicos-4(E)-en-1-yne has been achieved through double elimination of chloride intermediates 8 and 11,which were prepared from acetylenic alcohol intermediates 1 and 10.
1998, 9(4): 369-371
Abstract:
Under physiological conditions, γ-aminobutyric acid poorly crosses the blood-brain barrier. It is likely that a non-toxic derivative of γ-aminobutyric acid which enters the brain easily will have useful anticonvulsant activity. 16 derivatives of γ-aminobutyric acid with an imine link to a lipophilic carrier were prepared and tested for anticonvulsant activity; six compounds show anticonvulsant activity.
Under physiological conditions, γ-aminobutyric acid poorly crosses the blood-brain barrier. It is likely that a non-toxic derivative of γ-aminobutyric acid which enters the brain easily will have useful anticonvulsant activity. 16 derivatives of γ-aminobutyric acid with an imine link to a lipophilic carrier were prepared and tested for anticonvulsant activity; six compounds show anticonvulsant activity.
1998, 9(4): 373-375
Abstract:
1-Hydroxyl acetylation of 10-deacetylbaccatin III was achieved by removing the neighboring bulky 2-benzoyl group and oxidizing 2-hydroxyl group to a ketone function, but attempted reductive cleavage of 1-acetoxy gave rearranged products under different conditions with or without proton source.
1-Hydroxyl acetylation of 10-deacetylbaccatin III was achieved by removing the neighboring bulky 2-benzoyl group and oxidizing 2-hydroxyl group to a ketone function, but attempted reductive cleavage of 1-acetoxy gave rearranged products under different conditions with or without proton source.
1998, 9(4): 377-379
Abstract:
Six antigenic peptides of Sm26/2 glutathione S-transferase of schistosoma mansoni have been predicted according to their hydrophilicity, flexibility, accessibility, charge distribution and β-turn in the secondary structure by the determination of its primary structure, and synthesized by solid phase method. Two of them showed good antigenicity by Dot-ELISA. They would be candidate peptides of synthetic anti-schistosomal vaccine.
Six antigenic peptides of Sm26/2 glutathione S-transferase of schistosoma mansoni have been predicted according to their hydrophilicity, flexibility, accessibility, charge distribution and β-turn in the secondary structure by the determination of its primary structure, and synthesized by solid phase method. Two of them showed good antigenicity by Dot-ELISA. They would be candidate peptides of synthetic anti-schistosomal vaccine.
1998, 9(4): 381-384
Abstract:
We report here a new strategy for revealing the Claisen rearrangement of allyl phenyl ether occurring in the gas phase by in situ GC/MS technique. The Ciaisen rearrangement has been observed when allyl phenyl ether passed through the capillary column at certain temperatures. The relative proportion of rearrangement products is dependent on the temperature of the capillary column and the substituents on the phenyl ring.
We report here a new strategy for revealing the Claisen rearrangement of allyl phenyl ether occurring in the gas phase by in situ GC/MS technique. The Ciaisen rearrangement has been observed when allyl phenyl ether passed through the capillary column at certain temperatures. The relative proportion of rearrangement products is dependent on the temperature of the capillary column and the substituents on the phenyl ring.
1998, 9(4): 385-387
Abstract:
The fluorescence emission wavelength [λmax(em)] values of three types of benzaldehyde derivatives, namely, ethylene acetals (1-Ys), 4-nitrophenylhydrazones (2-Ys) and phenylhydrazones (3-Ys), have been measured. Correlation analyses by the dual-parameter equation show that the λmax(em) values of 1-Ys are mainly affected by the spin-delocalization effects of the substituents, while those of 2-Ys are mainly affected by the polar effects. However, those of 3-Ys are independent of the substituents.
The fluorescence emission wavelength [λmax(em)] values of three types of benzaldehyde derivatives, namely, ethylene acetals (1-Ys), 4-nitrophenylhydrazones (2-Ys) and phenylhydrazones (3-Ys), have been measured. Correlation analyses by the dual-parameter equation show that the λmax(em) values of 1-Ys are mainly affected by the spin-delocalization effects of the substituents, while those of 2-Ys are mainly affected by the polar effects. However, those of 3-Ys are independent of the substituents.
1998, 9(4): 389-391
Abstract:
In this paper, it is shown that pterodonoic acid may or may not have the structure of 3-oxoeudesma-4, 11-dien-12-oic acid 1 by comparison of their spectral data. But it is certainly not 10-epi-3-oxoeudesma-4, 11-dien-12-oic acid 2, which is synthesized from dihydrocarvone 3.
In this paper, it is shown that pterodonoic acid may or may not have the structure of 3-oxoeudesma-4, 11-dien-12-oic acid 1 by comparison of their spectral data. But it is certainly not 10-epi-3-oxoeudesma-4, 11-dien-12-oic acid 2, which is synthesized from dihydrocarvone 3.
1998, 9(4): 393-395
Abstract:
Urinary metabolites of icariin, present in Epimedium, were investigated using rats. In the urine of rats administered icariin orally, two major metabolites were detected, which were identified as icariside II and icaritin by means of spectral data.
Urinary metabolites of icariin, present in Epimedium, were investigated using rats. In the urine of rats administered icariin orally, two major metabolites were detected, which were identified as icariside II and icaritin by means of spectral data.
1998, 9(4): 397-400
Abstract:
We studied the factors affecting the framework aluminium distribution in the ZSM-5 structure by hydrothermal treatment under different conditions. 27A1MASNMR, XPS and chemical analysis revealed that with steaming at lower water vapor pressure, the framework aluminium located at the external surface is less stable. Steaming at higher water vapor pressure is beneficial in removing the framework A1 in HZSM-5, and especially helpful in removing that located at the internal surface of HZSM-5. By changing steaming conditions, one may control the framework aluminium distribution in the HZSM-5 structure.
We studied the factors affecting the framework aluminium distribution in the ZSM-5 structure by hydrothermal treatment under different conditions. 27A1MASNMR, XPS and chemical analysis revealed that with steaming at lower water vapor pressure, the framework aluminium located at the external surface is less stable. Steaming at higher water vapor pressure is beneficial in removing the framework A1 in HZSM-5, and especially helpful in removing that located at the internal surface of HZSM-5. By changing steaming conditions, one may control the framework aluminium distribution in the HZSM-5 structure.
1998, 9(4): 401-402
Abstract:
A long decay luminescent powder based upon the strontium aluminum oxide system with Eu2+ as the activator was produced. It was found that the variation of the molar ratio of A1 to Sr leads to a change in emission color. The two emission centers responsible for the color change have been identified.
A long decay luminescent powder based upon the strontium aluminum oxide system with Eu2+ as the activator was produced. It was found that the variation of the molar ratio of A1 to Sr leads to a change in emission color. The two emission centers responsible for the color change have been identified.
1998, 9(4): 403-406
Abstract:
A two-step electrodeposition method was developed to prepare hydroxyapatite/metal composite coatings. Hydroxyapatite coatings were fabricated by electrochemical deposition and post-treatment with alkaline solution, and then cobalt was electrodeposited to form hydroxyapatite/cobalt composite coatings to improve its mechanical properties of bonding strength.
A two-step electrodeposition method was developed to prepare hydroxyapatite/metal composite coatings. Hydroxyapatite coatings were fabricated by electrochemical deposition and post-treatment with alkaline solution, and then cobalt was electrodeposited to form hydroxyapatite/cobalt composite coatings to improve its mechanical properties of bonding strength.
1998, 9(4): 407-410
Abstract:
The morphology and structure of the syndiotactic polystyrene (sPS)/atactic polystyrene(aPS) blends with various compositions have been studied by means of DSC, optical microscopy, SAXS,and WAXD. The results show that aPS is miscible with amorphous region of sPS. There is no macroscopic evidence that aPS forms separated domains in the blends. The decrease in crystallinity of sPS in the blends implies segregation of the aPS to the interflbrillar regions of the spherulites of sPS. The constancy of interlamellar distance and melting points indicates that the fibrillar structural units of sPS is unchanged on addition of aPS to sPS, and the unchanging parameters of the sPS unit cells mean that aPS does not enter the unit cells of sPS.
The morphology and structure of the syndiotactic polystyrene (sPS)/atactic polystyrene(aPS) blends with various compositions have been studied by means of DSC, optical microscopy, SAXS,and WAXD. The results show that aPS is miscible with amorphous region of sPS. There is no macroscopic evidence that aPS forms separated domains in the blends. The decrease in crystallinity of sPS in the blends implies segregation of the aPS to the interflbrillar regions of the spherulites of sPS. The constancy of interlamellar distance and melting points indicates that the fibrillar structural units of sPS is unchanged on addition of aPS to sPS, and the unchanging parameters of the sPS unit cells mean that aPS does not enter the unit cells of sPS.
1998, 9(4): 411-414
Abstract:
The stabilization energies of substituted lithium carbene cations were calculated by using ab initio molecular orbital theory, and the relationship between the stabilization energies and molecular orbitals was discussed. The substituents with n donor engender strong stabilization to CH2Li+. The calculations show the Y-C* bond lengths of cations become shorter and H-Y bond lengths longer than those of corresponding neutral molecules.
The stabilization energies of substituted lithium carbene cations were calculated by using ab initio molecular orbital theory, and the relationship between the stabilization energies and molecular orbitals was discussed. The substituents with n donor engender strong stabilization to CH2Li+. The calculations show the Y-C* bond lengths of cations become shorter and H-Y bond lengths longer than those of corresponding neutral molecules.
