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A new era for organic synthesis—highlights of the recent progress
WU Yikang, WU Yu-Lin
Front. Chem. China. 2007, 2 (3): 227-264.
https://doi.org/10.1007/s11458-007-0046-0
The major progress in organic synthesis since 2005 is briefly surveyed in two parts. The first part deals with some of the most impressive advances in the synthetic methodology, which includes: (1) metal-mediated synthetic reactions, with an emphasis on the olefin metathesis and gold-mediated reactions; (2) free radical-based organic synthesis; (3) synthetic transformations performed in a one-pot manner involving either tandem reactions or multicomponent reactions; (4) asymmetric reactions catalyzed by metal and organo-catalysts. The major advances in total synthesis of some complex natural products with significant biological activities are presented in the second part, with detailed illustrations of ten selected molecules, including dragmacidin F, abyssomicin C, 11-acetoxy-4-deoxyasbestinin D, pentacycloanammoxic acid, UCS1025A, (−)-merrilactone A, nigellamine A2, (+)-saxitoxin, and Tamiflu (an artificially designed natural product-like molecule). An array of complicated structures of the natural products synthesized over the last two years is also listed to serve as a convenient lead to the original literature for the prospective interested readers.
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Preparation and characterization of nanotube Li-Ti-O by molten salt method
PEI Xianru, WANG Xiaodong, ZHANG Shunli, ZHANG Jingwei, YANG Jianjun, JIN Zhensheng
Front. Chem. China. 2007, 2 (3): 265-269.
https://doi.org/10.1007/s11458-007-0047-z
Nanotube Li-Ti-O compound with high surface (198.6 m2 · g-1) was prepared by a method involving the treatment of nanotube Na2Ti2O5 · H2O in molten LiNO3 and characterization by means of transmission electron microscopy (TEM), energy-dispersive spectra (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetry-differential thermal analysis (TG/DTG). Results show that the nanotube Li-Ti-O compound prepared by this method involves two crystal phases: spinel Li2Ti2O4 and anatase LixTiO2 (x<0.1). Li+ exhibits different Li1s binding energy in the two crystal phases. In ambient air, the Li-Ti-O compound adsorbs water easily, and the chemically adsorbed water is difficult to remove below 400?C.
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Quantitative analysis of nicotinic acid, nicotinamide and 3-cyanopyridine in industrial effluent by high performance liquid chromatography
TSANG Po Keung, ZENG Lixuan
Front. Chem. China. 2007, 2 (3): 270-273.
https://doi.org/10.1007/s11458-007-0048-y
A rapid and reliable high performance liquid chromatographic(HPLC) method for the simultaneous determination of heterocyclic compounds, namely nicotinic acid, nicotinamide, and 3-cyanopyridine, in industrial effluent is described. A Φ4.6 mm×150 mm, 5 μm C-18 reversed phase stationery phase, and a methanol-acetonitrile-water tertiary mobile phase (20:20:60 v/v) were used for separation. The detection wavelength of a diode array (DAD) was set at 216 nm with a bandwidth of 16 nm. Phenol was used as an internal standard. The regression equations revealed a linear relationship between the concentration of the analytes injected and the peak area detected by DAD. The limits of detection (S/N = 3) ranged from 0.70 to 1.18 mg L-1, the recoveries ranged from 87% to 102% and the precision expressed as % RSD intra-day and inter-day varied from 0.9 to 3.9 and 1.2 to 5.6, respectively. This method is rapid, sensitive and suitable for the monitoring of nicotinic acid, nicotinamide, and 3-cyanopyridine in effluent of related pharmaceutical manufacturing plants.
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Preparation, characterization and photocatalytic activity of visible light driven chlorine-doped TiO2
LONG Mingce, CAI Weimin, CHEN Heng, XU Jun
Front. Chem. China. 2007, 2 (3): 278-282.
https://doi.org/10.1007/s11458-007-0050-4
A novel chlorine-doped titanium dioxide catalyst with visible light response was prepared by hydrolysis of tetrabutyl titanate in hydrochloric acid. The catalyst samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Results showed that the doped element of Cl lowered the temperatures of phase transformation of TiO2 from amorphous to anatase and from anatase to rutile. The absorption edge of chlorine-doped TiO2 calcined at 300vH shifted to visible light region. X-ray photoelectron spectroscopy results proved that chlorine existed in the TiO2 crystal lattice as anion. The photocatalytic degradation of phenol showed that under visible light (λ>400 nm) irradiation, the chlorine-doped TiO2 calcined at 300vH displayed the best performance, the degradation ratio of phenol was 42.5% after 120 min.
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Generalization of in-situ polymerization method for preparing core-shell polymeric nanospheres and hollow spheres
ZHANG Youwei, ZHAO Jiongxin, WANG Jiaye, JIANG Ming
Front. Chem. China. 2007, 2 (3): 287-291.
https://doi.org/10.1007/s11458-007-0052-2
According to the new method of preparing core-shell nanospheres developed by our group, by using two monomers, 2-hydroxypropyl methacrylate(HPMA) and vinyl acetate(VAc), two kinds of core-shell nanospheres with poly(?-caprolactone) (PCL) as the core and crosslinked poly(2-hydroxypropyl methacrylate) (PHPMA) or poly(vinyl acetate) (PVAc) as the shell were successfully prepared under similar conditions. After degrading the PCL cores of the two kinds of nanospheres by lipase, the corresponding crosslinked poly(methyl acrylic acid) hollow spheres and crosslinked poly(vinyl alcohol) hollow spheres were obtained. Results indicate that the new method we proposed for preparing core-shell polymeric nanospheres via in-situ polymerization can be generalized to a certain extent, and it is suitable for many systems provided the monomer used is soluble in water, while its corresponding polymer is insoluble in water.
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Synthesis and crystal structure of inclusion compounds: Trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid with boric acid and tetrabutylammonium salt
YANG Yuan, LI Qi, ZHANG Jinnan, SONG Xiaohong, LUO Surong
Front. Chem. China. 2007, 2 (3): 296-302.
https://doi.org/10.1007/s11458-007-0054-0
Two new inclusion compounds (n-C4H9)4N+C18H13O4- &middo; B(OH)3 (1) and (n-C4H9)4N+C18H13O4- (2) were prepared and characterized by X-ray crystallography. Crystal data: compound 1, monoclinic P2(1)/c, a = 1.569 9(1) nm, b = 0.995 5(6) nm,c = 2.293 3(1) nm, β = 109.962(3)º, Z = 4, and R1 = 0.0434, wR = 0.075 9; compound 2, monoclinic C2/c, a = 1.400 5(3) nm, b = 1.282 1(2) nm, c = 1.765 7(3) nm, β = 100.388(1)º, Z = 4, and R1 = 0.0584, wR = 0.096 6. In the crystal structure of 1, the tetramers formed by two trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (EADA) anions and two boric acid molecules were connected through O H…O hydrogen bonds to generate a channel type host lattice. The tetra-n-butylammonium cations were stacked to give two columns within each channel with cross-sectional size of about 2.30 nm×0.93 nm. In the crystal structure of 2, similar honeycomb host lattices with big size were also formed along the [101] direction by three-dimensional accumulation of EADA anions. The tetra-n-butylammonium cations were accommodated in a zigzag fashion within each channel.
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New bioactive triterpenoid from Oldenlandia cantonensis How
LAN Wenjian, LI Houjin
Front. Chem. China. 2007, 2 (3): 307-310.
https://doi.org/10.1007/s11458-007-0056-y
A new pentacyclic triterpenoid, urs-12-en-29α-oic acid-3β-ol (1), was obtained from the ethanol extract of Chinese herb Oldenlandia cantonensis How. The structure was elucidated by spectroscopy methods, including nuclear magnetic resonance (NMR) (1D and 2D), infrared spectroscopy (IR), and mass spectrometry (MS). 1 exhibited significant inhibitory activity against the human DNA topoisomerase I (hTopo I), the cancer cell lines BEL-7402 and MCG-803, with the IC50 values 12.0, 6.5, and 8.0 y8/mL, respectively. The volatile oil, the fraction of petroleum ether: EtOAc = 20:1 (V/V) on Si gel chromatography, was also quantitatively analyzed by gas chromatography mass spectrometry (GC-MS). As a result, 60 compounds were identified. Among them, the long chain aliphatics, terpenes and steroids, as the representative structure type, were found with percentages of 36.16%, 6.42% and 9.28%, respectively.
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Research on synthesis and action mechanism of polycarboxylate superplasticizer
WU Hui, GUO Huiling, LEI Jiaheng, ZHANG Rongguo, LIU Yong
Front. Chem. China. 2007, 2 (3): 322-325.
https://doi.org/10.1007/s11458-007-0060-2
The relationship between the structure and performance of polycarboxylate superplasticizer was analyzed. The respective functions of the structure units of the main and branched chains were discussed. The progress of synthesis and molecular structure design and synthesis of polycarboxylate superplasticizer were reviewed according to the difference in the structure unit of the main chain. Results indicated that their performance is related to the structure unit of the main and branched chains, as well as the position and species of functional groups. The polycarboxylate superplasticizer, which had suitable graft and block polymers of polyethylene glycol or polyoxyethylene, and a suitable sulfonic group, had small slump loss besides high water-reducing performance. On the other hand, the hydroxyl group at the end of the chain causes gelation easily. On the basis of the items mentioned above, as well as the source and cost of raw materials, esterification of polyethylene glycol and acrylic acid were first adopted using para-toluene sulfonic acid as catalyst, then polymerized with sodium sulfonate methacrylate. A certain amount of acrylic was added in order to regulate both the polymerization degree of the main chain and the ratio of carboxyl and sulfonic groups in the branched chain. As a result, the high performance superplasticizer has been synthesized (was obtained). The divergence of the cement plasma is about 200 mm when the addition amount of superplasticizer is 0.16%–0.20% of cement weight, and the ratio of the water and cement is 0.29.
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