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Recently, considerable attention has been paid to the development of new functionalized polymers to improve the fuel efficiency of vehicles by reducing the rolling resistance of tires to adhere to strict CO2 emission regulations. Accordingly, multifunctionalized (MF) reversible addition–fragmentation chain transfer (RAFT) emulsion styrene–butadiene rubbers (ESBR) were synthesized, in which chain-end and in-chain functionalization were performed simultaneously by introducing a third monomer (glycidyl methacrylate; GMA) using RAFT polymerization. Compared with GMA ESBR, in which GMA is introduced as a third monomer by conventional radical polymerization (CRP), there was an even distribution of GMA per chain in the MF-RAFT ESBR. After preparing the silica-filled compounds, vulcanizate structure analysis and mechanical property evaluation of the compounds were performed. The MF-RAFT ESBR prepared by RAFT polymerization exhibited superior in-chain functionalization efficiency compared with GMA ESBR prepared by CRP because of the even distribution of GMA and higher crosslink density. Consequently, MF-RAFT ESBR compound showed superior silica dispersion, abrasion resistance, and lower rolling resistance compared with the GMA ESBR compound.

The development of ultra-high-performance tires that satisfy fuel efficiency, traction, handling performance, and abrasion resistance has gained significant importance in the tire industry. Solution SBR has been used as a raw material, owing to its useful characteristics (e.g., narrow dispersity controllable microstructure and chain-end functionalization). In a recent improvement, emulsion SBR (ESBR), a high-molecular-weight compound with narrow dispersity, has been reported for application in the tire tread compounds. In particular, S,S-dibenzyl trithiocarbonate (DBTC) reversible addition-fragmentation transfer (RAFT) ESBR has exhibited excellent abrasion resistance and fuel efficiency in unfilled and carbon black–filled vulcanizates. However, owing to the symmetrical structure of DBTC RAFT ESBR, the polymer chain was shortened by the reaction of a silane coupling agent with trithiocarbonate, leading to poor abrasion resistance and fuel efficiency in the case of silica-filled vulcanizates. In this study, benzyl (4-methoxyphenyl) trithiocarbonate (BMPTC), an asymmetric RAFT agent that promotes unilateral polymer growth, was synthesized and used in the polymerization of BMPTC RAFT ESBR. Chain cleavage was not observed. Upon application to silica-filled vulcanizates, BMPTC RAFT ESBR exhibited improved abrasion resistance (by 9%), improved fuel efficiency (by 20%), and improved wet traction performance (by 10%) compared with the DBTC RAFT ESBR.

Elemental sulfur (S8) is an inexpensive chemical feedstock for polymeric materials but has the disadvantages of poor solubility in organic media and inferior physical properties in the elemental form. We report on the preparation of organosulfur chalcogenide hybrid inorganic/organic polymer (CHIPs) based on bifunctional norbornene comonomers using dynamic covalent polymerization (DCP). A poly(sulfur-random-styrene) (p(S-r-Sty)) resin was utilized to address the limited solubility/ miscibility of norbornene-containing comonomers in liquid sulfur. This report demonstrated the ability to expand the scope of organic comonomers to prepare organosulfur CHIPs from elemenatal sulfur using a combination of inverse vulcanization and dynamic covalent polymerization.

Resource and time consuming difficult procedures involving the preparation of antigen surface functionalized nanoparticles mimicking viruses for optimum immunogenicity have been the challenges for their actual application. In this context, we developed stable polymeric particles functionalized with Ni2+-NTA via the combination of RAFT emulsion polymerization and polymerization-induced self-assembly (RAFT-PISA), and mixed with recombinant H1 tagged with hexa-histidine (His6-H1) for one day to prepare the influenza-mimetic polymeric particles. The RAFT-PISA based polymer particles exhibited good structural stability while the Ni2+-NTA-functionality provided a perfect docking site for the controlled orientation of His6-H1. The His6-H1 protein immobilization with Ni2+-NTA of the particle was studied with time. In addition, we investigated the immune response of the synthesized vaccine against influenza with varying the mixing time. We expect our system would open new avenues for preparation of influenza-mimetic vaccines like by mixing of a ready-made surface-functionalized particle and recombinant hemagglutinin.

For InP-based QDs, the current technology does not outperform CdSe-based QDs in many respects, one of which is stability. The optical stability of QDs is closely related to their surface properties, so QDs often use organic ligands for surface protection. These organic ligands are dynamically attached and detached on the QD surface; during detachment, their surfaces are easily damaged and oxidized, thereby deteriorating their optical characteristics. Therefore, we have synthesized a ligand 1,2-hexadecanedithiol with a bidentate form, inducing one ligand to bind to the QD surface strongly through the chelate effect, as a good way to improve the stability of the QDs; thus, the PL stability of the green-light-emitting InP-based QDs was greatly increased. To confirm the existence of the dithiol ligand, we used thermogravimetric analysis/simultaneous thermal analysis-mass spectroscopy (TGA/STA-MS). After that, we applied the ligand to blue-light-emitting ZnSe QDs and red-light-emitting InP QDs, and for those two types of QD we also confirmed that the stability was increased. Additionally, we tested dithiol exchanged QDs at a high temperature of 150 °C, and the increase of stability was effective even in a high temperature condition.

Recently, research conducted on tread compounds with liquid butadiene rubber (LqBR) have been conducted in the tire industry. In particular, the introduction of functional groups into LqBRs is expected to lower hysteresis loss caused by the free chain ends of LqBR. To study this, LqBRs with functional groups at different positions were synthesized. The occurrences of in-chain and chain-end functionalization of functionalized LqBRs (F-LqBRs) were confirmed, the microstructure and functionalization efficiency of F-LqBRs were calculated through the characterizations. This novel functionalization technology was beneficial not only to immobilizing the free chain ends of LqBRs to the surfaces of silica to decrease the number of free chain ends, but also chemically bonding the LqBR chains on the base polymer through a crosslinking reaction to enhance the filler-rubber interaction. The effects of the functional group position and number of the free chain ends on the physical properties and hysteresis of the compounds were investigated by partially replacing the treated distillate aromatic extract (TDAE) oil with LqBR in silica-filled rubber compounds. The results showed that compounds that had applied DF-LqBR with both end functionalization performed better, including improving the silica dispersion, higher extraction resistance, and lower rolling resistance, than other F-LqBRs compounds.

We report on the chromatographic separation and characterization of living chains in polystyrene prepared by reversible addition–fragmentation chain-transfer (RAFT) polymerization. To achieve full ...

We report a method to directly introduce a hydroxyl group at the omega chain end of polystyrene prepared by atom-transfer radical polymerization. To achieve the quantitative conversion of the bromine group to a hydroxyl group, the transfer reaction of a carbocation with water was exploited. This transfer reaction is a well-known reaction in cationic polymerization. The quantitative conversion and chemical structures of the hydroxyl-terminated PS were characterized using 1H nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and high-performance liquid chromatography. In addition, alcohol-based compounds were used to introduce acetonide and propane groups into PS-Br. We introduce a facile method to convert the bromine end of the polymer into a hydroxyl group. For this, bromine-terminated polystyrene (PS-Br) was prepared by atom transfer radical polymerization. The bromine groups of the PS-Br could be directly converted to hydroxyl groups by using Ag+ as the Lewis acid in water/acetone. The conversion yield was investigated by 1H nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Different types of polymer chains generated during the nitroxide-mediated polymerization of styrene are separated for the first time, and their molecular weight distribution (MWD) is investigated. Living and dead chains are monitored during the reaction; specifically, two types of living chains derived from the initiation of the alkoxyamine (RT) and the self-initiation of styrene and dead chains present in the as-prepared polystyrene (PS). To distinguish between each polymer species, different numbers of hydroxyl groups are introduced onto the T and R groups of the alkoxyamine (one and two groups, respectively). Each living and dead chains is resolved according to the distinct number of hydroxyl groups on its chain-end using high-performance liquid chromatography. Molecular structures of the fractionated PS are characterized using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and 1 H nuclear magnetic resonance spectroscopy, and the results of which show two distinct initiation paths: one originating from RT and the other from the self-initiation of styrene. Molecular weight and MWD are measured using size-exclusion chromatography and reveal a narrow MWD for the living chains derived from RT. Contrastingly, a broad and skewed MWD is observed for the other living chains derived from the self-initiation of styrene and the dead chains.

A composite solid propellant which generates high propulsive force in a short time is typically composed of an oxidizer, a metal fuel powder and a binder. Among these, the binder is an important component. The binder maintains the mechanical properties of propellant grains and endures several thermal and mechanical stresses in the engine. Several studies have been reported for the development of energetic propellant binders for increasing the propellant&prime, s propulsive force. While several materials have been studied for the synthesis of energetic prepolymers, a nitramine-group-containing prepolymer is a suitable candidate because these types of prepolymers are less toxic and more cost-effective when compared to the traditional glycidyl azide polymers (GAP) and triazole-based prepolymers. Considering the lack of studies for the binder using a nitramine-group-containing prepolymers, we synthesized a nitramine-group-containing monomer and polymerized a nitramine-group-containing prepolymer. The prepolymer was then used for the preparation of the binder and its thermal and mechanical properties, as well as the effect of the plasticizer, were studied. The binder that was prepared using the prepolymer containing a nitramine-group showed very high elongation, tensile strength. Nitrate-ester (NE)-type plasticizer could reduce the glassy transition temperature (Tg)of the binder successfully. Also, high-energy is released due to the decomposition of the nitramine-group at around 245 &deg, C, thus exhibiting the efficiency of the nitramine-group-containing prepolymer as an excellent energetic binder material.

A polyring capable of reversible growth and dissociation is synthesized from a tricyclic polystyrene (PS) prepared by combining atom transfer radical polymerization of a 4-arm star-shaped PS and azide–alkyne click reactions. In the preparation of the tricyclic PS, a coupling agent containing a disulfide linkage is used in the click cyclization reaction. The reduction of the disulfide linkage in the tricyclic PS results in an 8-shaped PS with thiol groups which on oxidation leads to a high molecular weight polyring. The topology transformation between the polymers occurs via reversible redox reaction of disulfide/thiol. The high molecular weight of the polyring is realized due to the formation of flexible S–S linkage between the 8-shaped PSs. Their structures are confirmed by FT-IR, 1H NMR, SEC, and MALDI-TOF MS analyses. In addition, molecular weight control of the polyring according to polymer concentration has been confirmed through SEC analysis.

Recently, InP-based quantum dots (QDs) have received significant attention due to their usefulness in display applications, and the search for good optical properties has led to numerous reports on the testing of reaction variables. However, most researchers have precluded the most important anion precursors in their studies, instead of focusing only on tris(trimethylsilyl)phosphine(P(SiMe3)3, TMS3P) precursors. Due to its vulnerability to moisture, TMS3P is unstable and difficult to handle. In the current study, a new anionic precursor, tris(hexylthio)phosphine(THTP), is introduced for use with InP-based QDs. Owing to its activated phosphine and sulfur atoms, the THTP molecule is a dual anionic precursor for both InP and ZnS QDs. When THTP is reacted with indium and zinc precursors, InPZnS alloy QDs can be fabricated. To observe the synthesis mechanism and probe the intermediate, FAB-mass and 31P-NMR analyses were conducted, resulting in the identification of an intermediate of MW 504. Finally, the surface was coated with a ZnS shell to obtain the emission wavelength from 530 nm to 570 nm and a maximum quantum efficiency of 42% when a ZnI2 precursor was used.

An efficient direct phthalic anhydride-mediated one-pot glycosylation method employing anomeric hydroxy arabinofuranose as glycosyl donor and triflic anhydride as activating agent has been developed. This method afforded the desired di- and oligoarabinofuranosides in good yields even in gram scale glycosylation when t-butylphthalic anhydride was used. Moreover, our new method can be further extended to the syntheses of repeating oligoarabinofuranoside and tetradecasaccharide arabinan motif found in mycobacterial cell wall.

In this study, we investigated the direct synthesis of primary arylamines from aryl iodides and bromides by Cu-catalyzed amination using ammonium hydroxide (27% NH 3 in H 2 O) as nucleophile. In this article, two protocols are described: (1) a variety of aryl halides were treated with CuI (10 mol %) and DMEDA (15 mol %) in NH 4 OH/DMSO, or (2) with only CuI (10 mol %) in NH 4 OH/PEG300. In each case, the desired primary arylamines were obtained in excellent yields. Although DMEDA and PEG have previously been employed as a ligand or solvent, respectively, the substrates were limited or additional ligands were required for successful conversion. Notably, our new protocols do not require additional inorganic bases, whereas previous methods have used a base. As such, these new protocols are one of the most simple, convenient, and efficient methods that have been reported, to date.

A series of bicyclic polystyrenes of different molecular weights was synthesized in one-pot by atom transfer radical polymerization followed by click chemistry. The bicyclic polystyrenes were formed simultaneously with branched polystyrene impurities due to side reactions during click coupling. The pure bicyclic polystyrenes were obtained by selective precipitation. The purity of bicyclic polystyrenes before purification was determined by Gaussian multiple peak fitting from SEC trace. The bicyclic polymers were characterized by SEC, 1H NMR, and FTIR spectroscopy. Open image in new window

Redox-initiated reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerizations are successfully conducted with an employment of trithiocarbonate-based macro-RAFT agents and surfactant. Two macro-RAFT agents-hydrophilic poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMA27 ) and amphiphilic poly(poly(ethylene glycol) methyl ether methacrylate)-b-polystyrene (PPEGMA27 -b-PS33 )- are examined for the miniemulsion polymerization of styrene. The use of PPEGMA27 (in the presence of sodium dodecyl sulfate (SDS)) results in a slow polymerization rate with a broad particle size. In the absence of SDS, the use of PPEGMA27 -b-PS33 results in a broad particle size distribution due to its inability to form uniform initial droplets whereas the same amphiphilic block copolymer in the presence of SDS yields resulting products with a uniform particle size distribution. The latter exhibits a fashion of controlled polymerization with a high consumption of monomer (98% in 100 min) and a narrow molecular weight distribution throughout the polymerization. This is attributed to the formation of uniform droplets facilitated by SDS in a miniemulsion. The amphiphilic macro-RAFT agent is able to anchor efficiently on the monomer droplet or particle/water interface and form stabilized particles of well-defined PPEGMA27 -b-PS block copolymer, confirmed using dynamic light scattering and transmission electron micrographs.

Glucosylations and galactosylations of various acceptors with donors possessing an electron-withdrawing benzylsulfonyl, benzoyl, or acetyl group at the O-3 or O-4 position were performed. A β-directing effect by the benzylsulfonyl group at O-3 of the glucosyl donors and by the benzylsulfonyl and acyl groups at O-4 of the glucosyl donors was observed. In contrast, acyl groups at O-3 of the glucosyl donors and acyl groups at O-3 and O-4 of the galactosyl donors exhibited an α-directing effect. The α-directing effect is partly considered to remote participation of the acyl groups, whereas the β-directing effect is somewhat attributed to the S N 2-like reaction of the acceptor with the glycosyl triflate or the contact ion pair, which is stabilized by remote electron-withdrawing groups. Further evidence for the stability of the α-glycosyl triflates was determined by a low-temperature NMR study.

A series of bicyclic polystyrenes were prepared by combining atom transfer radical polymerization and click coupling reaction. To investigate effect of experimental parameters, bicyclic polymers were prepared by changing types of ligands for click chemistry, concentration of polymers and coupling agents, feed rate of polymers and coupling agents, concentration of catalyst, and types of coupling agents. Purities of bicyclic polymers were estimated from SEC traces by Gaussian multiple peak fitting and subsequent peak integration. The purity of bicyclic polystyrene was achieved up to 78% when the reaction was conducted using CuBr/PMDETA catalyst and coupling agent having electron withdrawing group in diluted condition by slow addition of precursor polymer and coupling agent.

We synthesized poly((furfuryl methacrylate)-co-(2-(dimethylamino)ethyl methacrylate)) (p(FMA-co-DMAEMA)) for the dispersion of single-walled carbon nanotubes (SWCNTs) while maintaining their high aspect ratios. The nanotubes' length and height were 2.0 μm and 2 nm, as determined by transmission electron microscopy and atomic force microscopy, respectively. Transparent conductive films (TCFs) were fabricated by individually dispersed long SWCNTs onto a flexible polyethylene terephthalate substrate. The sheet resistance (Rs) was 210 Ω □(-1) with 81% transmittance at a wavelength of 550 nm. To reduce their Rs, the TCFs were treated with HNO3 and SOCl2. After treatment, the TCFs had an Rs of 85.75 Ω □(-1) at a transmittance of 85%. The TCFs exhibited no appreciable change over 200 repeated bending cycles. Dispersing SWCNTs with this newly synthesized polymer is an effective way to fabricate a transparent, highly conductive and flexible film.

Polymeric networks were prepared through a 1,3-dipolar cycloaddition of azide-bearing polymers with a variety of compounds having two or three terminal alkynes without solvents and catalysts. Dipolarophiles with an α-carbonyl underwent a very rapid Huisgen reaction within a few minutes to afford networks that were side-linked with triazole moieties. The reactivities of dipolarophiles were estimated by using frontier molecular orbital energies. To avoid the formation of defects in elastically ineffective networks, all polymer chain-ends were linked with urethane moieties, and very small quantities of azides were reacted with the dipolarophiles to link the pendent groups with the triazoles. Because the crosslinking densities of the energetic networks were inversely proportional to the reactivity of the dipolarophiles to the azides, the less reactive alkynes provided better mechanical properties to the networks prepared using the Huisgen cycloaddition reaction compared to the more reactive alkynes.

We designed and synthesized a polymeric dispersant for use with single-walled carbon nanotubes (SWCNTs). Poly((furfuryl methacrylate)-co-(2-(dimethylamino)ethyl methacrylate)) (p(FMA-co-DMAEMA)) was synthesized, and its solubility was tuned by the quaternization of a tertiary amine. Quaternized p(FMA-co-DMAEMA) (p(FMA-co-QDMAEMA)) changed the dispersibility of SWCNTs in various polar solvents, such as ethylene glycol (EG), methanol (MeOH), water and dimethylformamide (DMF). The chemical structures of the synthesized and modified polymeric dispersants were confirmed using 1H NMR. The dispersion quality of SWCNTs by p(FMA-co-QDMAEMA) was estimated using a particle stability analyzer, zeta-potential, UV-vis-NIR spectroscopy, transmission electron microscopy, and atomic force microscopy. The diameters and degree of defects of the dispersed SWCNTs were estimated using Raman spectroscopy. The dispersed SWCNTs in EG and MeOH display heights between 1.45 and 1.78 nm and a diameter of 1.17 nm, which corresponds to 1 or 2 bundled SWCNTs.

The 1,2,3-triazole crosslinked polymers with potential use as a binder system in solid rocket propellants were prepared by mixing of an azide chain-ends diazide prepolymer, a dipolarophile curing agent, which act as a crosslinker, and a plasticizer at C C/N 3 ratio of 1.1. A wide range of the plasticizer ratios were investigated: 0–300 wt% for the polycaprolactone (PCP) and polycaprolactone ether (PCE) prepolymer based binders, and 0–500 wt% for the polyethylene glycol (PEG) prepolymer based binder. Even at high amounts of plasticizer, sufficient initial reactivity and good conversion were obtained, however the increase of viscosity was considerably delayed. Crystalline domains of in the 1,2,3-triazole crosslinked polymers were effectively eliminated by the plasticizer. The tensile strength and modulus (100% and 300%, respectively) decreased with increasing of the amount of plasticizer whereas the elongation at the break was only modestly affected. PCP showed excellent elongation at the break compared to PEG at the same levels of plasticizer as well as good tensile strength. In contrast, the binder network prepared from the PCE prepolymer collapsed due to its low degree of crosslinking.

Although a number of methods have been developed for the selective oxidation of sulfides to sulfoxides, the need remains for alternative efficient, reliable strategies that can be generally applied to various sulfides and that use readily available reagents under mild reaction conditions. Herein, we report the use of urea–hydrogen peroxide adduct (UHP) and cyanuric chloride in CH3CN at room temperature to convert sulfides to sulfoxides in excellent yields. In particular, this protocol produced sulfoxides with aromatic rings bearing electron-withdrawing groups in excellent yields.

Bicyclic polystyrene was prepared by combining atom transfer radical polymerization and click chemistry. The bicyclic polymer was separated from concurrently produced acyclic (branched) polymers through fractional precipitation, and its purity was quantified by two-dimensional liquid chromatography analysis. The structure of bicyclic polymer was characterized by SEC, MALDI–TOF MS, 1H NMR, and FT-IR.

The crosslinking density of polymer can be quantitatively calculated by the Flory-Rehner equation using the swelling experimental data and the lattice constant β1 of interaction parameter (χ) in this equation should be chosen have used cautiously. This β1 is the experimental data by rule of thumb, and researchers have used little different values respectively. Generally, the average molecular weight between crosslink points Mc in the Flory-Rehner equation and the Mooney-Rivlin equation have the same value, and β1 can be calculated when the Mc in the Flory-Rehner equation is given. Therefore, in this research, firstly we calculated the Mc using the selected β1 (=0.34) and the swelling experimental data of 1,2,3-triazole polymer from the Flory-Rehner equation, secondly the Mc from the Mooney-Rivlin equation is calculated by the tensile experimental data, and finally two Mc were compared. As a result, two Mc values were almost the same, and it was proved that the β1 (=0.34) was selected properly.

Although a number of methods have been developed to reduce sulfoxides to sulfides, many of these processes are limited by side reactions, low yields, poorly available reagents, or harsh reaction conditions. We recently studied the reaction of various sulfoxides with SOCl2 and Ph3P. We were able to obtain the corresponding sulfides in excellent yields (>90%) when aliphatic and aromatic sulfoxides were treated with SOCl2 as a catalyst and Ph3P in THF at room temperature.

We carried out hydrazine-free, surfactant-free synthesis of noble metal/graphene nanocomposites. The reduction of the noble metals and GO was carried out simultaneously in hot water using ascorbic acid as a reductant. In the noble metal/graphene nanocomposites of Pd, Pt, Au, and Ag nanoparticles, the GO and metal salts were reduced completely by this synthetic method. In addition, the Pd/graphene nanocomposites showed good catalytic activity in the Suzuki coupling reaction and could be reused many times without loss of catalytic activity.

C-carbamoyl-1,2,3-triazoles have recently attracted much interest due to their potent biological activity. While synthesizing C-carbamoyl-1,2,3-triazoles by the copper(I)-catalyzed 1,3-dipolar cycloaddition of organic azides 1 and acetylenic amides 2, we found that the expected 1,2,3-triazole products 3 were obtained as the only products in excellent yields when CuSO4 and sodium ascorbate were used as the Cu(I)-catalyst. Surprisingly, the unexpected bistriazole products 4 were one of the major products obtained along with the 1,2,3-triazoles 3 when using a direct Cu(I)-catalyst such as CuI or CuBr.

Cysteamine (1) was reported many years ago to reversibly inhibit lentil seedling amine oxidase, through the formation of a complex with thioacetaldehyde, the turnover product of 1. Herein, cysteamine (1) and its analogs 2-(methylamino)ethanethiol (3) and 3-aminopropanethiol (6) were found to be reversible inhibitors of bovine plasma amine oxidase (BPAO), but 2-(methylthio)ethylamine (7) was determined to be a weak irreversible inhibitor of BPAO. Based on our results, indicating the necessity of a sulfhydryl-amine for reversible inactivation of BPAO, the failure of inhibited BPAO to recover activity after gel filtration, the first-order kinetics of activity recovery upon dialysis, and 2,4,6-trihydroxyphenylalanine quinine (TPQ) cofactor transformation which indicated from the results of phenylhydrazine titration and substrate protection, we propose a mechanism for the reversible inactivation of BPAO by 1 involving the formation of a cofactor adduct, thiazolidine, between BPAO and 1.

A convenient and efficient one-pot sequence has been developed for the synthesis of C-carbamoyl-1,2,3-triazoles from alkyl bromide using (i) sodium azide, (ii) methyl propiolate and copper iodide, and (iii) amines, zirconium tert-butoxide, and 1-hydroxybenzotriazole, under microwave irradiation. The sequential reactions in one-pot provided the desired C-carbamoyl-1,2,3-triazoles in excellent yields.

A series of halophenols was prepared by the reaction of bis(hydroxyphenyl)methanes with effective halogenating agents such as bromine and sulfuryl chloride. One of these compounds, a biologically active halophenol--2,2',3,3'-tetrabromo-4,4',5,5'-tetrahydroxydiphenylmethane (1)--frequently isolated from red algae, was synthesized for the first time. Other halophenols included several novel compounds, together with known derivatives that were synthesized from the phenolic intermediates, bis(3,4-dihydroxyphenyl)methane (5) and bis(2-hydroxyphenyl)methane (14). All of the synthesized compounds were tested for antimicrobial activity against Gram-positive, Gram-negative bacteria and fungi. The preliminary structure-activity relationship was investigated in order to determine the essential structural requirements for their antimicrobial activity. Of all these halophenols, 2,2',3,3',6-pentabromo-4,4',5,5'-tetrahydroxydiphenylmethane (8) was found to be the most active against Candidaalbicans, Aspergillusfumigatus, Trichophytonrubrum, and Trichophytonmentagrophytes while 3,3',5,5'-tetrachloro-2,2'-dihydroxydiphenylmethane (18) exerted a powerful antibacterial effect against Staphylococcusaureus, Bacillussubtilis, Micrococcusluteus, Proteusvulgaris, and Salmonellatyphimurium.

Conceptually new, enantiomerically pure bicyclic tetrahydrofuro[1,2-a]-A-ring phosphine oxides (+)-4 and (−)-4 were successfully prepared from methyl 2-pyrone-3-carboxylate and (S)- or (R)-2-(tert-butyldimethylsilyloxy)methyl-2,3-dihydrofuran, respectively. In addition, (2′-hydroxymethyl)tetrahydrofuro[1,2-a]-25-hydroxyvitamin D3 3a and 3b as new A-ring-modified analogs of the natural hormone 1α,25-dihydroxyvitamin D3 were readily synthesized by using Lythgoe-type coupling of the A-ring phosphine oxides (+)-4 and (−)-4 with C,D-ring ketone (+)-5.

Adsorption of ( S )–(+)– O -acetylmandelic acid on gold nanoparticle surfaces was examined by means of surface-enhanced Raman scattering. The adsorbate was presumed to bind to the surface via the carboxylate functional group due to the presence of symmetric stretching bands at ∼1350 cm −1 . Nearly identical spectral features to those of phenylacetic acid in conjunction with the disappearance of the C O stretching band at ∼1700 cm −1 were exhibited in the SERS spectra. These observations suggest scission of the carboxyl group into a benzyl radical intermediate on gold nanoparticle surfaces.

The concept of lactonization-mediated and related glycosylations led us to develop new methods of glycosylation such as the 2'-carboxybenzyl (CB) glycoside method, the glycosyl pentenoate/phenylselenyl trifluoromethanesulfonate (PhSeOTf) method, and the glycosyl aryl phthalate method. Highly stereoselective beta-mannopyranosylations were achieved by employing the CB glycoside and the glycosyl pentenoate/PhSeOTf methods. The CB glycoside method was also utilized for stereoselective 2-deoxyglycosylation, beta-arabinofuranosylation, and alpha-galactofuranosylation. In addition, these lactonization-mediated methods of glycosylation were employed for the synthesis of complex oligosaccharides. In particular, the CB glycoside method was successfully applied to the synthesis of repeating oligosaccharide subunits of the O-polysaccharide of the lipopolysaccharide from Danish Helicobacter pylori strains and Escherichia coli 077, the synthesis of oligoarabinofuranosides in mycobacterial cell walls, and the total synthesis of antineoplastic agelagalastatin.

The PhSeOTf promoted glycosylations of various glycosyl acceptors with mannosyl pentenoates and glucosyl pentenoates as glycosyl donors afforded corresponding disaccharides in high yields. And the present glycosyl pentenoates/PhSeOTf method showed that the complete α-selective mannosylation of secondary alcohol acceptors was achieved with 2,3,4,6-tetra- O -benzyl- d -mannopyranosyl pentenoate to give α-disaccharides in good yields.

The total synthesis of agelagalastatin, an antineoplastic glycosphingolipid, has been achieved. The synthesis involved an alpha-selective glycosylation of the ceramide moiety with the trisaccharide fluoride. The trisaccharide component was constructed employing the CB glycoside method which permitted a completely alpha-stereoselective galactofuranosylation.

The synthesis of the suitably protected form (1) of the tetrasaccharide repeat unit, →2)-α-D-Manp-(1→2)-β-D-Manp-(1→3)-α-D-GlcpNAc-(1→6)-α-D-Manp-(1→ (A), of the O-antigen polysaccharide of the lipopolysaccharide from Escherichia coli O77 has been accomplished by latent–active glycosylation employing the 2′-carboxybenzyl (CB) gly coside method. In addition to previously used latent glycosyl donors, 2′-(benzyloxycarbonyl)benzyl (BCB) glycosides, new latent glycosyl donors, 2'-(allyloxycarbonyl)benzyl (ACB) glycosides, have been introduced as a direct precursor for the active CB glycosides. We also demonstrate that 4,6-O-benzylidene-2-azido-2-deoxy-α-D-mannopyranoside (7) has been readily prepared from D-glucosamine in good yield.Key words: Escherichia coli O77, glycosylation, 2′-carboxybenzyl (CB) glycosides, 2′-(allyloxycarbonyl)benzyl (ACB) glycosides, glycosyl donor.

Urea-hydrogen peroxide adduct is a more reactive oxidant for the selective oxidation of sulfides to sulfoxides than H2O2 when utilized with cyanuric chloride as an activator.

[reaction: see text]. A reliable and generally applicable direct method for the stereoselective beta-arabinofuranosylation employing a 2'-carboxybenzyl arabinofuranoside as the glycosyl donor has been established. The acyl-protective group on glycosyl acceptors is essential for the beta-stereoselectivity. The power of the present acceptor-dependent glycosylation method was demonstrated by the efficient synthesis of the octaarabinofuranoside in arabinogalactan and lipoarabinomannan found in mycobacterial cell wall.

The development of an efficient and stereoselective glycosylation methodology has been a major concern in synthetic organic chemistry in the past a decade due to the important biological functions of complex oligosaccharides and glycoconjugates. Devising new glycosyl donors and developing new activation systems for the existing donors resulted in major advances in this area. For example, several glycosylation methodologies using the efficient glycosyl donors such as thioglycosides, glycosyl sulfoxides, glycals, glycosyl trichloroacetimidates, n-pentenyl glycosides, and glycosyl fluorides have been available. In addition, there have been recent reports regarding the development of glycosylation methods via new glycosyl donors and the application of existing glycosyl donors in novel activation systems. However, there still remains a need for more efficient and generally applicable new glycosylation methodology. In our previous endeavors, we reported a novel type of glycosyl donors, the 2’-(benzyloxycarbonyl)benzyl (BCB) glycoside and the 2’-carboxybenzyl (CB) glycoside A, as shown in Figure 1 for the stereoselective β-mannopyranosylation and the 2-deoxyglycosylation. We applied this methodology to the synthesis of a trisaccharide and tetrasaccharide. More recently, we have also reported the synthesis of the glycosyl benzyl phthalate C and its use as a new type of glycosyl donor. Although the glycosyl benzyl phthalate C proved to be the efficient glycosyl donor, there still remains a need for improvement. Thus, it is desirable to conduct the glycosylation more efficiently and at lower temperature in order to control the stereochemistry of the product and to keep acid-labile reactants or products intact under the acidic condition resulting from the use of TMSOTf. We envisaged that certain glycosyl aryl phthalates D might be more reactive than C so that the glycosylation might be conducted at lower temperature. Herein we describe the synthesis of a new type of glycosyl donors, the glycosyl aryl phthalate D and report that the glycosylation with glycosyl p-bromophenyl phthalates could be conducted under milder condition than that with glycosyl benzyl phthalates.

An efficient and practical route for large-scale synthesis of 2-deoxy- l -ribose starting from l -ascorbic acid was developed in eight steps without chromatographic purification for all intermediates. Additionally, (2S,3R)-3,4-epoxy-1,2-O-isopropylidenebutane-1,2-diol, a versatile intermediate in carbohydrate synthesis, was also prepared readily in excellent yield as a key intermediate.