Glycosyl alkoxythioimidates as complementary building blocks for chemical glycosylation

It is reported that S-glycosyl O-methyl phenylcarbamothioates (SNea carbamothioates) have a fully orthogonal character in comparison to S-benzoxazolyl (SBox) glycosides. This complete orthogonality was revealed by performing competitive glycosylation experiments in the presence of various promoters. The results obtained indicate that SNea carbamothioates have a very similar reactivity profile to that of glycosyl thiocyanates, yet are significantly more stable and tolerate selected protecting group manipulations. These features make the SNea carbamothioates new promising building blocks for further utilization in oligosaccharide synthesis.     

Generation and cyclization of unsaturated carbamoyl radicals derived from S-4-pentynyl carbamothioates under tin-free conditions

The radical reaction of benzenethiol with S-4-pentynyl carbamothioates provides a valuable protocol for the tin-free generation of carbamoyl radicals, which arise from intramolecular substitution at sulfur by the initial sulfanylvinyl radicals. This procedure can be usefully employed to achieve N-benzylcarbamoyl radical 5-exo and 4-exo cyclizations leading, respectively, to pyrrolidinones and azetidinones, although, for the latter, it seems of lesser utility. Novel evidence is presented that N-tosyl-substituted carbamoyl radicals display a peculiar tendency to yield the corresponding isocyanate by beta-elimination of the tosyl radical.     

Synthesis of sulfur containing analogues of the soluble guanylate cyclase inhibitor 8-bromo-4H-[1,2,4]oxadiazolo[3,4-c][1,4]benzoxazin-1-one NS2028

Sulfur analogues of the soluble guanylate cyclase (sGC) inhibitor NS2028 1a are synthesized. Treating 8-bromo-2H-benzo[b][1,4]oxazin-3(4H)-one oxime (6) with 1,1′-thiocarbonyldiimidazole (1.1 equiv) gave the carbamothioate 8-bromo-4H-[1,2,4]oxadiazolo[3,4-c][1,4]benzoxazine-1-thione (3a) in 83% yield. Alternatively reacting NS2028 1a with P₂S₅ (0.5 equiv) affords the carbamothioate 3a in 80% yield. Similar treatment of 8-aryl substituted NS2028 analogues 1b-d with P₂S₅ gave the carbamothioates 3b-d in 64-91% yields. Although quite stable, the carbamothioates 3a-d could be thermally isomerized in the presence of Cu (10 mol %) to afford the thiocarbamates 4a-d in high yields. Interestingly, in the case of carbamothioate 3a Pd and In metals also facilitated the isomerization. Furthermore, treatment of the thiocarbamates 4a-d with P₂S₅ (0.5 equiv) affords the carbamodithioates 5a-d in 72-89% yields. All new compounds are fully characterized including single crystal X-ray data for carbamothioate 3a and thiocarbamate 4a. Finally, a mechanism is proposed for the carbamothioate to thiocarbamate isomerization.     

高效膜色谱的发展和应用

对新兴的高效膜色谱的基质材料、膜形态、分离机理以及应用进行了综述,并对其用于对映体分离作了展望。共７６篇。     

改善高氯卤化银乳剂的高照度性能

本实验制备了高氯卤化银立方体系列乳剂和高氯卤化银(100)晶面T颗粒乳剂,对高氯卤化银立方体乳剂进行了不同种类掺杂剂的掺杂试验.通过测定以上各乳剂在常规曝光和高照度曝光下的照相性能,表明了在高氯卤化银乳剂中掺杂碘化物、掺杂铱络合物和掺杂浅电子陷阱掺杂剂都可以不同程度地改善乳剂的高照度性能,几种改进措施的结合效果更好.     

Crystallization and reinforcement of poly (vinylidene fluoride) nanocomposites: Role of high molecular weight resin and carbon nanotubes

The effect of high molecular weight resin and multi-walled carbon nanotubes (MWCNTs) on the crystallization, rheological and dynamic mechanical properties of poly (vinylidene fluoride) (PVDF) composites was investigated. A synergetic effect of the high molecular weight resin and MWCNTs on the nucleation in the crystallization process of the matrix has been observed, and their contributions to the crystallization of the matrix are two-sided. The composites containing both the high molecular weight resin and MWCNTs have much higher crystallization peak temperatures but lower crystallinity, especially for samples with high MWCNT content. For the isothermal crystallization at relative high temperatures, higher Avrami exponent and shorter half-time of crystallization are observed for the composites containing both the high molecular weight resin and MWCNTs. The introduction of the high molecular weight resin not only reinforces the matrix, but also promotes the dispersion of MWCNTs. The reinforcement and synergetic nucleation effects of the high molecular weight resin and MWCNTs were also confirmed by dynamic mechanical analysis.     

SPEEK/PES-C、SPEEK/SPES-C共混质子交换膜研究

通过在磺化聚醚醚酮(SPEEK,DS=61.68%)中分别混入酚酞型聚醚砜(PES-C)、磺化酚酞型聚醚砜(SPES-C,DS=53.7%)制备出SPEEK/PES-C、SPEEK/SPES-C共混质子交换膜.结果表明,共混的两种聚合物之间均具有较好的相容性.PES-C、SPES-C的混入能有效降低膜的溶胀及甲醇透过,且随着共混量的增加,这种作用越趋明显.纯SPEEK膜在75℃左右溶解,而SPEEK/PES-C(30 wt%)、SPEEK/SPES-C(30 wt%)共混膜在80℃时溶胀度仅为22.5%、26.32%.在室温至80℃范围内,纯SPEEK及共混膜的甲醇透过系数都在10-7 cm2·s-1数量级上,远小于Nation[R]115膜.在饱和湿度下,温度大于90℃时,SPEEK/PES-C(20 wt%)共混膜电导率超过Nation[R]115膜;温度大于110℃时,SPEEK/SPES-C(30 wt%)共混膜电导率与Nafion[R]115膜相当,达到0.11 S·cm-1.高电导率,低透醇系数以及明显提高了的可使用温度表明该类共混膜有望在DMFC中使用.     

MCM-48介孔分子筛的高压合成

采用正硅酸乙酯（TEOS）作硅源,十六烷基三甲基溴化铵（CTAB）为模板剂,在高压 （约7 MPa）和373 K下合成了MCM-48介孔分子筛.用XRD、氮气吸附及29Si MAS NMR对样品 进行了表征.与常压合成的相比,高压下合成的MCM-48具有更高的热稳定性和水热稳定性.2 9Si MAS NMR结果表明,高压有利于分子筛孔壁的聚合,导致分子筛结构更加完善,从而使 其具有更高的稳定性.     

Lipid lowering effects of high linoleate and high alpha-linolenate diets in rats and mice. Consequence of long-term feedings.

Diets high in linoleate (safflower oil) or high in alpha-linolenate (perilla oil) were fed to rats for 11 months, and the effects of the diets on plasma and tissue lipids were compared. The plasma levels of total cholesterol (Cho), phospholipids (PL) and triacylglycerol (TG) were significantly lower in the high alpha-linolenate group than in the high linoleate group, the differences being more than 30% in the levels of total Cho and TG. The diets had differential effects on the lipid contents of major tissues: the TG level in muscle was higher but both the TG level in depot fat and the PL level in muscle were lower in the high alpha-linolenate group than in the high linoleate group. In order to clarify whether or not the hypolipidemic effect of the high alpha-linolenate diet was due to changes in the distribution of lipids among tissues, whole body lipids were estimated in mice fed these diets for 5 months. The whole body Cho content was significantly lower, by 28%, in the high alpha-linolenate group compared with the high linoleate group, but the total lipid content, PL and neutral lipids were similar between the groups. Our results indicate that the high alpha-linolenate diet has a more potent cholesterol lowering effect in plasma and body tissue than the high linoleate diet; interestingly, whole body TG levels are similar but tissue distributions of TG are different between the two dietary groups.     

Highly diastereoselective Friedel-Crafts reaction of furans with 8-phenylmenthyl glyoxylate

The Friedel-Crafts reaction of (1R)-8-phenylmenthyl glyoxylate with variously substituted furans was found to be efficiently promoted by SnCl(4) or magnesium salts with high diastereoselectivities. MgBr(2) performs especially well under simple, undemanding conditions, giving both high yields and high diastereoselectivities (>90%). The reaction afforded chiral substituted furan-2-yl-hydroxyacetic acid esters, compounds of potentially high synthetic interest. [reaction: see text]     

Poly(3,4-ethylenedioxythiophen)/Poly(4-styrenesul-fonate): Thin Films and Microfibers

This Feature Article describes our recent researches on processing poly(3,4-ethylenedioxythiophene /poly(4-styrenesulfonate) (PEDOT/PSS) colloidal dispersion into thin films which exhibit high conductivity and high transparency, and into microfibers which exhibit high conductivity and high mechanical strength. The state-of-the-art thin films and microfibers are expected to utilize to sophisticated touch screens and wearable electronic devices as organic transparent electrodes and woven electric circuits, respectively.     

Water-Soluble Polypeptides with Elongated, Charged Side Chains Adopt Ultra-Stable Helical Conformations

Water-soluble polypeptides adopting α-helical conformations with unprecedented high helicities were obtained by elongating the charge-containing side chains of the constituent amino acids to allow the terminal charges to be situated distally from the peptide backbone. Poly(γ-(4-aminoethylthiopropoxyl)-benzyl-(L)-glutamate) (PAOBLG-AET) with a charge-peptide backbone distance of 17 σ-bonds exhibited a remarkably high helical content (81%) at a degree of polymerization as low as 10. The helical conformations of these short polypeptides were very stable against various harsh, protein-denaturing conditions, such as extreme pH, high temperature, and high salt or urea concentrations.     

Highly diastereoselective heterogeneously catalyzed hydrogenation of enamines for the synthesis of chiral beta-amino acid derivatives

Pure (Z)-enamines readily prepared from beta-ketoesters and amides using (S)-phenylglycine amide were hydrogenated with very high diastereoselectivities (up to 200:1) using heterogeneous catalysis. Hydrogenolytic cleavage of the (S)-phenylglycine amide afforded the corresponding chiral beta-aminoesters and amides. The high geometrical purity of the (Z)-enamine and a simple activation procedure for the PtO2 catalyst are essential in achieving high selectivity.     

Synthesis and characterization of alkaline‐soluble triazine‐based poly(phenylene sulfide)s with high refractive index and low birefringence

High‐refractive‐index (high‐n) polymers (HRIPs) with a high optical transparency are highly needed in advanced optoelectronic devices. In this work, we report the synthesis and characterization of a series of high‐n, transparent, totally colorless, and high‐sulfur‐containing poly(phenylene sulfide)s (PPSs) bearing a triazine unit. Two new triazine monomers T1 and T2 with hydroxyl and tert‐butyl acetate side chains, respectively, were designed and synthesized to develop PPSs with high‐n and high alkaline solubility. These PPSs were prepared by the single‐phase polycondensation from T1 / T2 and commercial aromatic dithiols such as 4,4′‐thiobisbenzenethiol ( TBT ) and benzene‐1,3‐dithiol ( BDT ), achieving very high‐n up to 1.7530 at 633 nm, a high optical transparency (T% > 90% @400 nm) and low birefringence (Δn = 0.0014–0.0080), and exhibiting high potential on the application of high‐n photoresists. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 724–731     

High refractive index adamantane‐based silicone resins for the encapsulation of light‐emitting diodes

The encapsulation of high power light emitting diode (LED) needs the silicone resins to have relative high refractive index and thermal‐aging properties. Herein, high refractive index adamantane‐based phenyl epoxy‐silicone (APES) resins for LED encapsulation were synthesized by the sol‐gel condensation of 1‐adamantane methanol propyltrimethoxysilane‐3‐urethane, γ‐(2,3‐epoxypropoxy)propytrimethoxysilane and diphenylsilanediol. These adamantane‐based silicone resins have multifunctional groups including adamantyl group, phenyl group, and epoxy group in order to meet the various requirements for LED encapsulation. Importantly, the adamantane group in the silicone resins benefits for high refractive index and anti‐thermal properties. These APES resins were characterized by proton nuclear magnetic resonance and Fourier transform infrared spectroscopy. When APES resins were cured by methylhexahydrophthalic anhydride, they showed relatively high refractive index of 1.56, high hardness, and high thermal resistance. The encapsulated LED demonstrated high adhesion properties by red‐ink tests. These merits make adamantane‐based silicone resins promising candidates as LED encapsulation materials.     

高硒及高硒高维生素E合用对十二月龄大鼠血清MDA和ALT的影响

给动物喂食高Se、高vitaminE、高Se高vitaminE合用饲料 ,探讨单独及合用高Se、高vitaminE对十二月龄动物血清中MDA和ALT的影响。结果显示 ,与对照组比较 ,单独及合用高Se、高vitaminE均可显著降低血清中MDA的含量 (P <0 0 1 ) ,高vitaminE尚能使血清中ALT水平升高 (P <0 0 5 ) ,而高Se高vitaminE合用则可纠正高vitaminE引起的血清中ALT水平的升高     

A general and efficient method for the selective synthesis of beta-hydroxy sulfides and beta-hydroxy sulfoxides catalyzed by gallium(III) triflate

Gallium(III) triflate-catalyzed ring opening of epoxides affords beta-hydroxy sulfides with high regioselectivity and chemoselectivity in high yields (84-97%) under solvent-free conditions. Additionally, a simple, efficient, and environmentally benign one-pot procedure for the synthesis of beta-hydroxy sulfoxides in sole water has been developed for the first time. The process, promoted by a H2O2-Ga(OTf)3 system, affords beta-hydroxy sulfoxides in high yields (81-94%) and high chemoselectivity without any detectable overoxidation to beta-hydroxy sulfones. The catalyst could be recovered easily after the reactions and reused without evident loss of activity.     

Application of capillary electrophoresis in peptide research.

Comparison of high performance liquid chromatograms (HPLC) with capillary electrophoresis shows the latter to be superior in many cases owing to rapid separation, high resolution and high sensitivity. This is demonstrated with two examples (i) the isolation of natural peptides from bovine tissue and (ii) characterization of a synthetic peptide mixture with the natural sequence (fragment) of the human immunodeficiency virus (HIV) transmembrane glycoprotein gp 41 env.     

低浓度部分水解聚丙烯酰胺/柠檬酸铝交联体系剪切稳定性研究

采用粘度法、核孔膜过滤和动态光散射(DLS)法,研究了高分子量低浓度的部分水解聚丙烯酰胺(HPAM)与柠檬酸铝(AlCit)反应所形成的交联体系的剪切稳定性和HPAM剪切降解后与AlCit反应所形成的体系的封堵性能及降解机理.研究结果表明,低浓度的HPAM与AlCit反应所形成的交联聚合物体系随剪切速率增加,其对1.2μm的核孔膜的封堵能力降低.HPAM稀溶液剪切降解后再与AlCit反应,低剪切速率对其封堵性能影响较小,而高剪切速率会使得其封堵性能大大降低.HPAM/AlCit交联体系和HPAM剪切降解后形成的交联体系的封堵性能下降的原因是HPAM/AlCit交联体系中交联聚合物线团(LPC)尺寸和HPAM中高分子线团的尺寸变小.     

Chiral sulfoxides as neutral coordinate-organocatalysts in asymmetric allylation of N-acylhydrazones using allyltrichlorosilanes

Sulfoxides were first introduced to the allylation of N-acylhydrazones with allyltrichlorosilanes as effective neutral coordinate-organocatalysts (NCOs). Both high diastereo- and enantioselectivity were attained when optically active chiral sulfoxides were used. Asymmetric crotylations using (Z)- and (E)-crotyltrichlorosilanes showed a high level of stereospecificity (Z --> anti and E --> syn) with high enantioselectivity.