pK(a)-directed host-guest assemblies: rational analysis of molecular adducts of 2,4-diamino-6-methyl-1,3,5-triazine with various aliphatic dicarboxylic acids

Molecular adducts of 2,4-diamino-6-methyl-1,3,5-triazine (1) have been prepared with various aliphatic dicarboxylic acids. The molecular complexes (1 a-1 i) thus formed by co-crystallizing 1 with oxalic, malonic, succinic, fumaric, acetylene dicarboxylic, glutaric, thiodiglycolic, diglycolic, and adipic acids have been found to give two types of host-guest assemblies that have voids or channels in a three-dimensional arrangement. The different types of host-guest arrangement appear to result from differences in the acidity of the dicarboxylic acids, that is, acids with pK(a)<3.0 give host networks that consist of 1 and the corresponding acid with water or solvent molecules of crystallization present as guests, whereas acids with pK(a)>3.0 exist as guests in voids in a host network formed by 1. The former arrangement is observed in adducts 1 a, 1 b, 1 e, and 1 h and the latter arrangement is found in adducts 1 c, 1 d, 1 f, 1 g, and 1 i.     

Triptycene-derived oxacalixarenes as new wheels for the synthesis of [2]rotaxanes: acid-base- and metal-ion-switchable complexation processes

A pair of triptycene-derived oxacalixarenes, 1a and 1b, containing two naphthyridine subunits have been synthesized by a convenient one-pot approach. Macrocycles 1a and 1b are diastereomers, with 1a being a cis isomer with a boat-like 1,3-alternate conformation and 1b being a trans isomer with a curved boat-like conformation in the solid state. Both 1a and 1b have fixed conformations in solution at room temperature, as revealed by variable-temperature (1)H NMR spectroscopy experiments. It was found that oxacalixarenes 1a and 1b could both form 1:1 [2]pseudorotaxane-type complexes with paraquat derivatives with different functional groups in solution and in the solid state, which resulted in the further synthesis of a pair of novel isomeric [2]rotaxanes. Moreover, the controlled dethreading and rethreading processes of the [2]pseudorotaxanes were also easily achieved by acid-base stimuli or Hg(2+) association/dissociation.     

From BN-Naphthalenes to Benzoborole Dianions

The synthesis of benzoborole dianions by alkali metal reduction of BN-naphthalene derivatives via a ring-contraction strategy has been developed. Reduction of 1-alkynyl 2,1-benzazaborine 1 a in Et₂O led to the elimination of alkynyllithium with the formation of 1-amino-1-benzoborole trilithium salt 2 a , whereas reduction of 1-phenyl 2,1-benzazaborine 1 c in THF yielded 1-phenyl-1-benzoborole dilithium salt 2 c with the elimination of ArNHLi. The trilithium and dilithium salts 2 a and 2 c have been fully characterized. Treatment of trilithium salt 2 a with Et₃NHCl led to the selective protonation of the amino lithium to afford the dilithium salt 2 aH , which could be cleanly oxidized to 1-amino-1-benzoborole 3 in an excellent yield. Reaction of 1-phenyl-1-benzoborole dilithium salt 2 c with MeI yielded the lithium borate 4 c , which is luminescent both in solution and in the solid state.     

S1P1-selective in vivo-active agonists from high-throughput screening: off-the-shelf chemical probes of receptor interactions, signaling, and fate

The essential role of the sphingosine 1-phosphate (S1P) receptor S1P(1) in regulating lymphocyte trafficking was demonstrated with the S1P(1)-selective nanomolar agonist, SEW2871. Despite its lack of charged headgroup, the tetraaromatic compound SEW2871 binds and activates S1P(1) through a combination of hydrophobic and ion-dipole interactions. Both S1P and SEW2871 activated ERK, Akt, and Rac signaling pathways and induced S1P(1) internalization and recycling, unlike FTY720-phosphate, which induces receptor degradation. Agonism with receptor recycling is sufficient for alteration of lymphocyte trafficking by S1P and SEW2871. S1P(1) modeling and mutagenesis studies revealed that residues binding the S1P headgroup are required for kinase activation by both S1P and SEW2871. Therefore, SEW2871 recapitulates the action of S1P in all the signaling pathways examined and overlaps in interactions with key headgroup binding receptor residues, presumably replacing salt-bridge interactions with ion-dipole interactions.     

羟丙基-β-环糊精对1-羟基芘与牛血清白蛋白相互作用的影响

在模拟生理条件下,利用荧光光谱、圆二色光谱和紫外-可见吸收光谱探究了羟丙基-β-环糊精(HPCD)对1-羟基芘(1-OHPyr)与牛血清白蛋白(BSA)相互作用的影响及其相关机制.结果表明,291 K下HPCD可使1-OHPyr与BSA的结合常数降低为1.45×10~5L/mol;导致1-OHPyr-BSA体系中BSA的α-螺旋含量恢复,色氨酸(TRP)残基周围微环境的极性变化减弱;致使1-OHPyr及BSA的荧光寿命均延长,且二者的结合距离增大.初步研究结果表明,HPCD与1-OHPyr的包络作用是HPCD影响BSA与1-OHPyr结合的主要原因.     

Syntheses of new model compounds related to an antigenic epitope from Bupleurum falcatum L. and their distributions in various ganglioside-phospholipid monolayers

6-N-[2-(Tetradecyl)hexadecanamido]hexyl beta-D-glucopyranosyluronic acid-(1-->6)-beta-D-galactopyranosyl-(1-->6)-beta-D-galactopyranoside (1) and its clustering compound (2) carrying a tetravalent sugar unit, which are new model compounds related to a major antigenic epitope from antiulcer pectic polysaccharide of Bupleurum falcatum L., were synthesized and the distributions of 1 and 2 in mixed ganglioside (GM1, GD1a or GT1b)/phospholipid (DPPC) monolayers were observed using atomic force microscopy (AFM). AFM images showed that 1 was distributed in the GM1, GD1a and GT1b region of the mixed monolayers, in which 1 was miscible with GD1a. Specific distribution of 1 was observed in the mixed GM1/DPPC monolayer. Compound 2 was miscible with GM1, while 2 formed associations with GD1a and GT1b in the mixed monolayers. The distribution mode of 1 and 2 was different among the mixed ganglioside/DPPC monolayers.     

C- and O-Alkylation with α-Haloketones of the Adamantane Series

Reactions of 1-adamantyl bromomethyl ketone and 1-(1-adamantyl)-3-bromo-2-propanone with acetylacetone and ethyl acetoacetate in a mixture of dry diethyl ether with anhydrous methanol in the presence of sodium methoxide afforded 3-(1-adamantylcarbonylmethyl)-2,4-pentanedione, ethyl 2-(1-adamantylcarbonylmethyl)-3-oxobutanoate, 4-acetyl-1-(1-adamantyl)-2,5-hexanedione, and ethyl 2-acetyl-5-(1-adamantyl)-4-oxopentanoate. The Knoevenagel-Cope reactions of 1-adamantyl bromomethyl ketone and 1-(1-adamantyl)-3-bromo-2-propanone with diethyl malonate yielded, respectively, diethyl 1-(1-adamantyl)-2-bromoethylidenemalonate and diethyl 1-(1-adamantylmethyl)-2-bromoethylidenemalonate. O-Alkylation of ethyl acetoacetate with 1-adamantyl bromomethyl ketone gave ethyl 3-(1-adamantylcarbonylmethoxy)-2-butenoate. Carboxylic acids reacted with 1-adamantyl bromomethyl ketone to form the corresponding 2-(1-adamantyl)-2-oxoethyl carboxylates.     

Palladium-catalyzed aminations of aryl halides with phosphine-functionalized imidazolium ligands

A series of 1-(2-diphenylphosphinoferrocenyl)ethyl-3-substituted imidazolium iodides [3-substituent = methyl (1a); isopropyl (1b); tert-butyl (1c); 1-adenosyl (1d); cyclohexyl (1e); 2,6-dimethylphenyl (1f); 2,4,6-trimethylphenyl (1g); 2,6-diisopropylphenyl (1h)] have been prepared and evaluated as ligands in the palladium-catalyzed aminations of aryl halides with various amines. The scope of the coupling process was carried out for various aryl bromides and chlorides with the catalysts generated in situ from a mixture of Pd(OAc)2 and in the presence of a base. NaO t Bu was found the choice of base in combination with dioxane, toluene, or DME as solvent, although NaOH or Cs2CO3 promoted the coupling of 4-bromotoluene with morpholine in moderate conversion. The steric hindrance from the 3-substituent of imidazolium in the hybrid-bidentate chelating system was found to be only beneficial to the substrates without ortho-substituents. The more sterically hindered 1d or 1h promoted the coupling of bromobenzene with morpholine in nearly quantitative conversion with 0.2 mol% of palladium loading in the presence of NaO t Bu at 110 degrees C, and 94% of conversion was afforded with the less sterical demanding 1a for a longer time. However, for the substrates with ortho-substituents, higher conversions were achieved with 1a. The Pd(OAc)2/1d catalytic system was also active for deactivated aryl chloride, and 71% isolated yield for the desired product was realized for coupling of 4-chloroanisole with morpholine at 2 mol% of catalyst loading. The developed catalyst system has been applied successfully to the synthesis of a key building block for a type of functional polymers.     

Synthesis of Functionalized 1-Alkenylboronates via Hydroboration-Dealkylation of Alkynes with Diisopinocampheylborane

Hydroborations of propargyl chloride, ethyl propiolate, 3-trimethylsilyloxy-1-butyne, 1,1-diethoxy-2-propyne, 1-iodo- and 1-bromo-1-hexyne, and 1-bromo-3-chloro-1-propyne with diisopinocampheylborane 1, followed by dealkylation of the isopinocampheyl groups with acetaldehyde provide the corresponding 1-alkenylboronates in high yields with high regioselectivity.     

Regio - and stereospecific halogenation of 7alogenoalkenes in liquid hydrogen fluoride

The products of bromo and chlorofluorination of E and Z-1,2-dichloroethylenes, 1, 3-dichloro-1-propenes, 1, 1-dichloro- ethylene and 1, 3-dichloro-2-fluoro-1-propene by N-bromosuccinimide and hexachloromelamine in anhydrous hydrogen fluoride have been studied. It was found that the reaction was in all cases 100% regio and 93–100% trans-stereospecific with the exception of E-1, 2-dichloro-ethylene, its trans-stereospecificity being 85%.Threo and erithro-1-bromo-1, 2-dichloro-2-fluoroethanes, 2-bromo-1, 3-dichloro-1-fluoropropanes and 1, 2, 3-trichloro-1-fluoro-propanes as well 1, 1, 2-trichloro-2-fluoroethane, 1-bromo-2, 2-dichloro-2-fluoroethane, 1, 2, 2-trichloro-2 fluoroethane, 1-bromo-1, 3-dichloro-2, 2-difluoropropane, and 1, 1, 3-trichloro-2,2-difluoropropane were obtained in 50–70% yield.The bromination of E and Z-1, 3-dichloro-1-propenes with molecular bromine in carbon tetrachloride in the dark is non-stereospecific and gives a mixture of erithro and threo-1, 2-dibromo-1, 3-dichloropropanes in the ratio about 1:1. However, the bromination reaction in anhydrous hydrogen fluoride solution proceeds with a high degree of stereospecificity (94–95%) and gives threo-1, 2-dibromo-1, 3-dichloropropane from Z and erithro-1, 2-dibromo-1, 3-dichloropropane from E-1, 3-dichloro-1-propene.The data obtained are considered in terms of an electrophilic mechanism of halogenoalkene halogenation in anhydrous hydrogen fluoride and a free-radical mechanism in carbon tetrachloride.     

Studies with Functionally Substituted Methylbenzotriazoles: Novel Synthesis of Functionally Substituted Pyrazolo[5,1‐c]‐1,2,4‐Triazines Benzotriazol‐1‐yl, 1‐Pyrazol‐4‐yl Benzotriazoles and 1‐Isoxazol‐4‐yl Benzotriazoles

1‐Benzotriazolylacetophenone 1 couples with aromatic diazonium salts to yield the corresponding coupling products 2 . Reaction of 1 with diazotized aminopyrazole afforded the benzotriazolylpyrazolo[5,1‐c][1,2,4]triazine 6 . Compound 1 condensed with DMFDMA to yield the enaminone 7 which reacted with hydrazines to yield the pyrazoles 8a,b . Isomeric pyrazoles 10 were synthesized via condensing 1 with phenyl‐hydrazine and subsequent condensation of the formed phenylhydrazone 9 with DMFDMA. Reaction of 7 with hydroxylamine afforded the isoxazole 11 which was converted into the nitrile 13 on reflux in dioxane in the presence of sodium hydride. Compound 13 was also directly obtained from reaction of 1 with 1‐cyanobenzo‐triazole. The reaction of 1 with hippuric acid and arylidenemalononitriles 18a‐c afforded the pyranone 17 and pyridine derivatives 23a‐c , respectively.     

Synthesis and reactivity of 3-(trichlorogermyl)propanoic acid and 3-(triphenylgermyl) propanoic acid

3-(Trichlorogermyl)propanoic acid (la) reacts with phenylmagnesium bromide in malar ratio 1:4 to give 3-(triphenylgermyl)propanoic acid (2a).In the compounds la and 2a theβ-carboxylic functional group shows some unusual properties when they react with excess of phenylmagnesium bromide.The compound la reacts with phenylmagnesium bromide in molar ratio 1:5 to give phenyl 2-(triphenylgermyl)ethylketone (3a) and in molar ratio 1:6 to give l,l-diphenyl-3-(triphenylgermyl)propanol (4a).The compound 2a reacts with phenylmagnesium bromide in molar ratio 1:2 to give 3a and in molar ratio 1:3 to give 4a also.Dehydration of the compound 4a with dilute hydrochloric acid seems especially easy.Moreover,the compound la reacted with phenylmagnsium bromide in molar ratio 1:6,then the mixture was treated with dilute hydrochloric acid to give 1,1-diphenyl-3-(triphenylgermyl)-1-propene (5a) in one pot reaction.Alkyl Ge-C bond in the compound 5a can be cleaved selectively by lithium aluminium hydride ( LiAlH4) in good yiel     

高密度燃料HDF-1与橡胶的相容性研究

报道了在室温和70 ℃下橡胶材料G402氟硅胶、丁腈胶5171、丁腈胶4170、贮囊橡胶用合成的高密度燃料HDF-1浸泡后性能如伸长率、邵尔硬度、重量、面积体积的变化，并与采用3号喷气燃料（RP-3）实验结果进行对照。用红外光谱测定了燃料浸泡前后橡胶组成的变化。实验结果表明，G402氟硅胶和贮囊对于HDF-1和RP-3有相近的相容性，丁腈胶5171对HDF-1的相容性比对RP-3的相容性稍差，丁腈胶4170对HDF-1的相容性比对RP-3的相容性更差的结果。因此，丁腈胶5171和丁腈胶4170不能用于HDF-1储存和输送，原使用RP-3系统的橡胶密封件不能直接使用HDF-1。     

Phase equilibrium and rheology of poly(1-trimethylsilyl-1-propyne) solutions

The phase equilibrium and rheological properties of poly(1-trimethylsilyl-1-propyne) solutions obtained with tantalum catalysts are studied. For three polymers with different molecular masses, phase diagrams are determined in a number of solvents. From these diagrams, the Hansen solubility parameters of poly(1-trimethylsilyl-1-propyne) are calculated by the method proposed in this work. Dilute solutions of poly(1-trimethylsilyl-1-propyne) behave as Newtonian liquids, whereas the viscosity of viscoelastic concentrated systems decreases as the shear rate grows. The molecular and rheological characteristics of studied poly(1-trimethylsilyl-1-propyne) samples are compared with the samples prepared with NbCl₅ catalysts. Poly(1-trimethylsilyl-1-propyne) obtained with a catalytic system involving tantalum pentachloride is characterized by high intrinsic viscosity and solution viscosity compared to poly(1-trimethylsilyl-1-propyne) prepared with niobium catalyst. The difference in properties is due to the dissimilar ratios of cis and trans units in the samples.     

Origins of the differences in solvation by alkanes and perfluoroalkanes Evidence from the S2-S0 spectra of jet-cooled van der Waals complexes of xanthione and azulene

The S₂-S₀ fluorescence excitation spectra ofxanthione (XT) and azulene (AZ) complexed with 1 or 2 molecules of the C₁ to C₁₀ n-alkanes and the C₁ to C₆ perfluoro-n-alkanes have been measured. The 1:1 complexes exhibit microscopic solvent shifts, Δ gn, which are larger for the alkanes than the corresponding perfluoroalkanes, despite the larger molecular polarizability of the latter. The values of Δ gn increase monotonically with carbon number of the adduct to C₁₀ in 1:1 n-alkane complexes with XT and to C₅ in 1:1 n-alkane complexes with AZ. However, Δ gn exhibits no further increase beyond C₂ in 1:1 perfluoro-n-alkane complexes with XT and beyond C₃ in 1:1 perfluoro-n-alkane complexes with AZ. The results are interpreted in terms of a model in which the n-alkanes stretch out along the long axis of the chromophore and ‘wet’ its surface whereas the perfluoro-n-alkanes with carbon numbers 3 away from the surface of the chromophore and are ‘non-wetting’.     

Head-to-head vinyl polymers. IV. Preparation and characterization of equimolar head-to-head copolymers of acrylic acid and its esters

The alternating copolymer of ethylene with maleic anhydride was esterified with a number of aliphatic alcohols to yield its monoesters, which correspond structurally to equimolar (1:1) head-to-head (h-h) copolymers of acrylic acid with alkyl acrylates. In addition, they were methylated with diazomethane to 1:1 h-h copolymers of methyl acrylate with alkyl acrylates. For comparison the 1:1 head-to-tail (h-t) copolymers of methyl acrylate with alkyl acrylates were prepared by radical copolymerizations. Some chemical, physical, and thermal properties of these 1:1 h-h and h-t copolymers were evaluated and compared. The softening and glass transition temperatures of the 1:1 h-h copolymers were somewhat higher than those of the corresponding 1:1 h-t copolymers, which indicated that the h-h replacements made the polymer chain stiffer and less flexible. The 1:1 h-h copolymers were also observed to degrade thermally at somewhat higher temperatures and with higher rates than the 1:1 h-t copolymers. The ratio of alcohol to monomer found in the pyrolysis products was higher for the 1:1 h-h than for its respective 1:1 h-t copolymer.     

H2CCC光谱性质的从头算研究

采用全活化空间自洽场方法(CASSCF)在C2v对称性和ANO-S基组水平下, 研究了H2CCC自由基及其阴阳离子的基态和低激发态性质. 为了进一步考虑动态电子相关效应, 采用多组态二级微扰理论(CASPT2)获得了更加精确的能量值. 计算得到X1A1 → 1A2, X1A1 → 1B1和X1A1 → 21A1在159.0, 216.5和476.4 kJ/mol处的激发可分别归因于π(b2)→π*(b1), n(a1)→π*(b1)和π(b1)→π*(b1)的跃迁, 理论波长与紫外吸收光谱得到的实验数据一致. 计算得到的电子亲和势与实验值也非常接近.     

Interaction and Interfacial Molecular Recognition of Calix[4] arene Derivatives Bearing Nucleobases for Complementary Nucleoside

The p-tert-butyl calix[4] arene derivatives la with uracils and 1b with adenines at the lower rim were synthesized.The Interaction between 1a and 1b in CDCl3 solution was demonstrated by ^1H NMR spectra.The interfacial molecular recognitions of la and 1b for the complementary nucleosides in aqueous subphases were investigated by Langmuir-Blodgett technique.     

Excess volumes of ternary mixtures of N,N-dimethylformamide-diethyl ketone-1-alkanols at 303.15K

Volume changes on mixing of ternary liquid mixtures of N,N-dimethylformamide and diethyl ketone with 1-alkanols have been measured as a function of composition at 303.15 K. The alkanols include 1-propanol, 1-butanol, 1-pentanol and 1-hexanol. The measured V^E values are negative in the mixtures of N,N-dimethylformamide, diethyl ketone and 1-propanol, or 1-butanol. The V^E data exhibits an inversion in sign in the mixture containing 1-pentanol and positive excess volumes are observed in the mixture containing 1-hexanol. The measured data are compared with predicted values based upon empirical relations. The excess volume for the binary mixture of N,N-dimethylformamide with diethyl ketone has been measured over the entire range of composition at 303.15 K. The V^E values are negative for the binary mixture.     

A Simple Structure-Switch Aptasensor Using Label-Free Aptamer for Fluorescence Detection of Aflatoxin B1

Aflatoxin B1 (AFB1) is one of the mycotoxins produced by Aspergillus flavus and Aspergillus parasiticus, and it causes contamination in foods and great risk to human health. Simple sensitive detection of AFB1 is important and demanded for food safety and quality control. Aptamers can specifically bind to targets with high affinity, showing advantages in affinity assays and biosensors. We reported an aptamer structure-switch for fluorescent detection of aflatoxin B1 (AFB1), using a label-free aptamer, a fluorescein (FAM)-labeled complementary strand (FDNA), and a quencher (BHQ1)-labeled complementary strand (QDNA). When AFB1 is absent, these three strands assemble into a duplex DNA structure through DNA hybridization, making FAM close to BHQ1, and fluorescence quenching occurs. In the presence of AFB1, the aptamer binds with AFB1, instead of hybridizing with QDNA. Thus, FAM is apart from BHQ1, and fluorescence increases with the addition of AFB1. This assay allowed detection of AFB1 with a detection limit of 61 pM AFB1 and a dynamic concentration range of 61 pM to 4 μM. This aptamer-based method enabled detection of AFB1 in complex sample matrix (e.g., beer and corn flour samples).