分散聚合水基聚苯胺乳胶微球制备与表征

水溶性空间稳定剂聚乙烯吡咯烷酮（PVP）存在时，采用分散聚合制备水溶性单分散的聚苯胺(PAn)乳胶粒子，采用透射电子显微镜（TEM）观察粒子形态及尺寸；利用紫外-可见吸收光谱对胶体分散体系进行表征.实验结果表明，当PAn含量较少（w< 16.78％）时， PAn-PVP复合乳胶粒子呈米粒状；当PAn含量较大（w >23.22％）时， PAn-PVP复合乳胶粒子呈球形.     

An efficient route for the preparation of a 21-fluoro progestin-16 alpha,17 alpha-dioxolane,a high-affinity ligand for PET imaging of the progesterone receptor

Two different synthetic routes were explored for the synthesis of fluoro furanyl norprogesterone (FFNP) 1, a high-affinity ligand for the progesterone receptor (PgR) that is being developed as a PET imaging agent for PgR-positive breast cancer. Both approaches proceed through a key intermediate, triol 5. The first approach, starting from keto-ketal 2, employed a dioxenyl group as a synthon for installing a corticosteroid side chain in keto-alcohol 4. The second approach, starting from propargylic acetate 12b, involved the application of a two-step method, a Pd(II)-catalyzed oxidative rearrangement followed by a base-catalyzed acetate rearrangement of the intermediate unsaturated acetate 13b, to generate the requisite corticosteroid side chain in keto-acetate 14b. This intermediate was further elaborated to the final product 1 via efficient dihydroxylation with potassium permangnate, furan acetalization with scandium triflate, and mesylation and fluorination reactions. The palladium-catalyzed route is considerably more efficient than the dioxene approach for the synthesis of key intermediate triol 5, and the scandium triflate-catalyzed acetalization, in particular, led to a considerable improvement in the overall yield of the endo furan acetal alcohol 16a. This route provides a major improvement in the overall yield of the final progestin target, FFNP 1.     

A Novel 3‐D Heterobimetallic Cyano‐bridged Coordination Polymer Incorporating Ag···Ag Interaction: [Cu(dien)Ag(CN)2]2[Ag2(CN)3][Ag(CN)2]

A three‐dimensional cyano‐bridged copper(II) complex, [Cu(dien)Ag(CN)₂]₂[Ag₂(CN)₃][Ag(CN)₂] ( 1 ) (dien = diethylenetriamine), has been prepared and characterized by X‐ray crystallography. Complex 1 crystallized in the monoclinic space group P2₁/n with a = 6.988(2), b = 17.615(6), c = 12.564(4) Å, β = 90.790(5)°. The crystal consists of cis‐[Cu(dien)]²⁺ units bridged by [Ag(CN)₂]^— to form a zig‐zag chain. The Ag atoms of the free and bridging [Ag(CN)₂]^— link together to form additional infinite zig‐zag chains with short Ag···Ag distances. The presence of Ag···Ag interactions effectively increases the dimensionality from a 1‐D chain to a 3‐D coordination polymer.     

聚对苯撑对苯二甲酰胺液晶的相态转变

本工作以H(?)ppler流变粘度计、退偏振光法及小角激光光散射法研究了聚对苯撑对苯二甲酰胺的浓硫酸溶液在不同浓度和温度下的粘性行为、光学性质和区域结构的变化,发现聚对苯撑对苯二甲酰胺的各向异性溶液在不同温度下呈现向列型液晶和胆甾型液晶特征,说明芳香聚酰胺的液晶体系与小分子液晶相类似,也具有多种中介相的转变现象。这里的中介相转变是由向列型转变为胆甾型,但不是直接的同时是一个单变性的相转变过程。     

Ab initio study of (13)C(alpha) chemical shift anisotropy tensors in peptides

This study reports magnitudes and the orientation of the (13)C(alpha) chemical shift anisotropy (CSA) tensors of peptides obtained using quantum chemical calculations. The dependency of the CSA tensor parameters on the energy optimization of hydrogen atom positions and hydrogen bonding effects and the use of zwitterionic peptides in the calculations are examined. Our results indicate that the energy optimization of the hydrogen atom positions in crystal structures is necessary to obtain accurate CSA tensors. The inclusion of intermolecular effects such as hydrogen bonding in the calculations provided better agreement between the calculated and experimental values; however, the use of zwitterionic peptides in calculations, with or without the inclusion of hydrogen bonding, did not improve the results. In addition, our calculated values are in good agreement with tensor values obtained from solid-state NMR experiments on glycine-containing tripeptides. In the case of peptides containing an aromatic residue, calculations on an isolated peptide yielded more accurate isotropic shift values than the calculations on extended structures of the peptide. The calculations also suggested that the presence of an aromatic ring in the extended crystal peptide structure influences the magnitude of the delta(22) which the present level of ab initio calculations are unable to reproduce.     

Neutron activation analysis of extractable organohalogens in milk from China

Instrumental neutron activation analysis (INAA) has been used for the determination of extractable organohalogens (EOX) in milk. The detection limits are 50 ng, 8 ng and 3.5 ng for Cl, Br and I, respectively. The EOX concentrations in milk samples from various regions of China were determined. Meanwhile, organochlorine pesticides residues were detected by gas chromatography. The concentrations of the EOX in the milk samples are decreasing in the order of EOCl >> EOBr > EOI, and EOCl accounts for 95% of the total EOX. The average concentration of EOCl in milk is 4.44 ·g/g expressed as fat weight basis, with the highest value of 17.6 ·g/g from South China. The mean concentrations of total HCH and DDT are 0.038 ·g/g and 0.046 ·g/g, respectively. Organochlorine pesticides account only for 1.6% of the EOCl, indicating the very high proportion of the unknown EOCl in the milk sample. This revised version was published online in August 2006 with corrections to the Cover Date.     

AIBN-initiated radical addition of gem-difluorinated alkyl iodides to alkynes and the Pd-catalyzed Sonogashira coupling reaction of E-phenyl difluoromethylene vinylic iodides with terminal alkynes

The addition of gem-difluorinated alkyl iodides to alkynes initiated by AIBN neatly gave the corresponding difluoromethylene vinyl iodides among which the stereoselectivity of aromatic acetylenes was high. The further coupling reaction of E-phenyl difluoromethylene vinyl iodides with terminal alkynes in the presence of catalytic palladium afforded the substituted difluorinated enynes.     

Copper-catalysed photoinduced decarboxylative alkynylation: a combined experimental and computational study

Redox-active esters (RAEs) as alkyl radical precursors have demonstrated great advantages for C–C bond formation. A decarboxylative cross-coupling method is described to afford substituted alkynes from various carboxylic acids using copper catalysts CuCl and Cu(acac)₂. The photoexcitation of copper acetylides with electron-rich NEt₃ as a ligand provides a general strategy to generate a range of alkyl radicals from RAEs of carboxylic acids, which can be readily coupled with a variety of aromatic alkynes. The scope of this cross-coupling reaction can be further expanded to aliphatic alkynes and alkynyl silanes using a catalytic amount of preformed copper-phenylacetylide. In addition, DFT calculations revealed the favorable reaction pathway and that the bidentate acetylacetonate ligand of the copper intermediate plays an important role in inhibiting the homo-coupling of the alkyne.

Redox-active esters (RAEs) as alkyl radical precursors have demonstrated great advantages for Cu-catalysed C–C bond formation.     

Increased throughput in quantitative bioanalysis using parallel-column liquid chromatography with mass spectrometric detection

The feasibility of quantitative bioanalysis by parallel-column liquid chromatography in conjunction with a conventional single-source electrospray mass spectrometer has been investigated using plasma samples containing a drug and its three metabolites. Within a single chromatographic run time, sample injections were made alternately onto each of two analytical columns in parallel at specified intervals, with a mass spectrometer data file opened at every injection. Thus, the mass spectrometer collected data from two sample injections into separate data files within a single chromatographic run time. Therefore, without sacrificing the chromatographic separation or the selected reaction monitoring (SRM) dwell time, the sample throughput was increased by a factor of two. Comparing the method validation results obtained using the two-column system with those obtained using the corresponding conventional single-column approach, the methods on the two systems were found to be equivalent in terms of accuracy and precision. The parallel-column system is simple and can be implemented using existing laboratory equipment with no additional capital outlays. A parallel-column system configured in this manner can be used not only for the within-a-run analysis of two samples containing two different sets of chemical entities, but also for the within-a-run analysis of two samples containing the same set of chemical entities.