Synthesis of dicarboxylate oligosaccharide multilayer terminal functionality upon poly(lysine) dendrimer scaffolding

A reactive three‐layered dendrimer containing carboxyl groups was synthesized by the coupling of dicarboxylic acid and a highly reactive, two‐layered glycopeptide dendrimer. Lactose, maltose, or maltotriose was reacted with the poly(lysine) dendrimer in its third and fourth generations by reductive amination and afforded two‐layered glycolysine dendrimers. The reaction was conducted in a borate buffer (pH 9.0). ¹H NMR, ¹³C NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analyses were applied for the determination of the structures of the products. When an excess amount of the oligosaccharide and a long reaction time were used, the degree of substitution increased to 1.5–2.0 against an amino group. For the preparation of highly reactive, multilayered dendrimers for an antigen carrier, C6 hydroxy groups of the oligosaccharides were selectively esterified by adipic acid and suberic acid to give 6‐O‐adipoyl oligosaccharide–poly(lysine) dendrimers and 6‐O‐suberoyl oligosaccharide–poly(lysine) dendrimers. The reactivity of these multilayered dendrimers was examined by a model reaction with phenylalanine ethyl ester. The dendrimer showed high reactivity, providing phenylalanine ethyl ester–dicarboxylate oligosaccharide–poly(lysine) dendrimers with a considerably high proportion of phenylalanine residues. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3622–3633, 2002     

Some studies on the solid solutions in the systems Sr2Nb2O7Eu2Nb2O7 and Sr2Ta2O7Eu2Ta2O7

Preparation of new solid solutions containing divalent europium have been tried in the systems Eu₂Nb₂O₇Sr₂Nb₂O₇ and Eu₂Ta₂O₇Sr₂Ta₂O₇. These solid solutions described as Eu_2xSr_2(1?x)M₂O₇ (M = Nb and Ta) exist in a pure orthorhombic phase in a limited region of x from 0 to about 0.5. The compounds with compositions close to Eu₂M₂O₇ exist but techniques have not been found to prepare them in pure form.     

Selective syntheses of metalated pyridines from two different unsymmetrical acetylenes, a nitrile, and a titanium(II) alkoxide

Cyclotrimerization of two different, unsymmetrical acetylenes and p-toluenesulfonylnitrile with a divalent titanium alkoxide reagent, Ti(O-i-Pr)4/2 i-PrMgCl, yielded single pyridyltitanium compounds in a highly selective manner. These metalated pyridines were confirmed by deuteriolysis to give the corresponding deuterated pyridines and underwent iodinolysis and copper-catalyzed alkylation to demonstrate their synthetic utility. Alternatively, a different type of cyclotrimerization of an alkynamide, terminal acetylenes, and alpha-alkoxynitriles mediated by the same titanium(II) alkoxide again proceeded in a highly selective manner to give single pyridines having a titanated side chain.     

Phenothiaphosphine-containing polyamides and polyesters

Phosphorus-containing polyamides and polyesters, which had tricyclic fused rings (phenothia-phosphine rings) in the main chain, were prepared and the properties of the resulting polymers were examined. These polymers were obtained at highly reduced viscosities in satisfactory yields by the polycondensation of 2,8-dichloroformyl-10-phenylphenothiaphosphine 5,5,10-trioxide with aromatic diamines or bisphenols. The polyamides and polyesters were soluble in polar aprotic solvents such as dimethylacetamide and N-methyl-2-pyrrolidone; the polyesters were also soluble in chloroform. The polymers exhibited good heat resistance. The phenothiaphosphine-containing polyamides and polyesters self-extinguished immediately when flame was removed and were highly flame-resistant. The polyester obtained from bisphenol A showed a limiting oxygen index value of 43.5.     

Electro-optic effects of colloidal crystals of polymer-modified silica spheres immobilized with gelator

Electro-optic responses of colloidal crystals consist of poly(maleic anhydride-co-styrene)-modified silica spheres (P(MA-ST)/SiO₂) in acetonitrile and the crystals immobilized with a gelator, N-benzyloxycarbonyl-L-isoleucilaminooctadecane (Z-L-Ile-C-18), are studied by reflected-light intensity measurements and time-resolved reflection spectroscopy. Application of an alternating electric field deforms P(MA-ST)/SiO₂ crystal lattices reversibly. The response waveforms from the crystals are dependent on the frequency and strength of the applied electric field; similar dependencies have been qualitatively observed for the colloidal crystals consisting of polystyrene or silica spheres in aqueous media in our previous studies. Both gelated and ungelated P(MA-ST)/SiO₂ crystals change the reflection intensity, however, the amplitude is larger for the latter. The small response for the gelated P(MA-ST)/SiO₂ crystals is attributed to the higher elastic modulus (G). The G value of the gelated P(MA-ST)/SiO₂ crystals in acetonitrile is estimated from the change in the inter-sphere distance to be 8.0 Pa, which is about 2.3 and 2.4 times larger than that for ungelated P(MA-ST)/SiO₂ crystals in acetonitrile and colloidal silica crystals in aqueous media, respectively.     

One-pot reductive amination of aldehydes and ketones with α-picoline-borane in methanol, in water, and in neat conditions

A one-pot reductive amination of aldehydes and ketones with amines using α-picoline-borane as a reducing agent is described. The reaction has been carried out in MeOH, in H₂O, and in neat conditions in the presence of small amounts of AcOH. This is a highly efficient and mild procedure that is applicable for a wide variety of substrates. In particular, this is the first successful demonstration that this type of reaction can be carried out in water and in neat conditions.     

Copolymerization of ethylene sulfide and carbon disulfide

Ethylene sulfide was found to copolymerize with carbon disulfide to give poly(ethylene trithiocarbonate) in the presence of Hg(SC₄H₉)₂, Zn(C₂H₅)₂, or Cd(C₂H₅)₂, which are well known as the effective catalysts for the coordinated anionic copolymerization of episulfides. The structure and the composition of the copolymer was determined by the infrared and NMR spectra. To establishe the mechanism of the copolymerization, the reaction of carbon disulfide and Hg(SC₄H₉)₂, and also the ring-opening polymerization of ethylene trithiocarbonate were examined. Carbon disulfide was found to insert easily into the metal-sulfur bond of Hg(SC₄H₉)₂ under the experimental conditions of the copolymerization. On the other hand, the ring-opening polymerization of ethylene trithiocarbonate did not take place with these catalysts, occurring only with the use of sulfuric acid. From these results, the mechanism of the copolymerization was discussed.     

Surface ionization detector with a supersonic free jet for gas chromatography some applications

A new design for a gas chromatographic surface ionization detector based upon hyperthermal positive surface ionization has been developed: There were two requirements: supersonic free jet nozzle and the high work function surface of Re-oxide. This detector, which is highly sensitive in response to all organic compounds, can be operated as an universal detector with an additional selectivity towards some species that have low ionization energy, but with selectivity to a much lesser degree than a conventional surface ionization detector. The minimum detectable amount of toluene is ca. 10⁻¹² g/s with a linearity greater than 10⁴. Some applications are demonstrated using three examples for the analysis of different formulations: (1), terpene mixture, (2), polycyclic aromatic hydrocarbon mixture and (3), alkyl alcohol mixture.     

Characteristics of complexes composed of sodium hyaluronate and bovine serum albumin

Complexes composed of sodium hyaluronate (NaHA) and bovine serum albumin (BSA) were studied to elucidate the exact composition of the complex, the phase separation, the electrophoretic mobility and the size using dynamic light scattering (DLS) and electrophoretic light scattering (ELS), etc. The phase diagram of the mixed solutions was determined. The complexes were soluble in neutral or weakly acidic pH regions and showed phase separation in the more acidic pH region. From the concentration of Na+ released from NaHA when it binds to BSA, the ratios of BSA to NaHA of the complexes were determined. In the region of soluble complexes, one BSA molecule was determined to bind with 15 carboxylic groups of NaHA and in the region of insoluble complexes to bind with 6 carboxylic groups. At the phase separation point, 117 BSA molecules bound with one NaHA molecule and 17% of the carboxylic groups of NaHA did not contribute to the binding of BSA. The sizes of the complexes decreased from several microm to several hundred nm as the binding ratio of BSA increases. Decreases in the viscosities of the mixed solutions were consistent with the decreases of the sizes. From these results, a model of complex formation is proposed.     

[2.2](2,6)Biphenylenophane and [2](2,6)Biphenyleno[2](2,6)naphthalenophane

Two cyclophanes, [2.2](2,6)biphenylenophane and [2](2,6)biphenyleno[2](2,6)naphthalenophane, were prepared.