Syntheses of pyrido[1,2-a][1,3,5]triazin-4-one C-deoxyribonucleosides

We achieved the syntheses of new C-deoxyribonucleosides bearing pyrido[1,2-a][1,3,5]triazin-4-one derivatives using palladium-catalyzed Heck-type coupling. Some of these C-deoxyribonucleosides were able to convert to phosphoramidite reagents, which can be used for DNA synthesizer. DNA oligomers including pyrido[1,2-a][1,3,5]triazin-4-one C-deoxyribonucleoside, which had 2-amino group were synthesized, and T_m values with a natural nucleoside were measured.     

Electrodialytic transport properties of anion-exchange membranes in the presence of α-cyclodextrin

Electrodialysis of mixed salt solutions, sodium chloride and sodium sulfate, and sodium chloride and sodium nitrate, was carried out in the presence of α-cyclodextrin using commercial anion-exchange membranes. It was confirmed by several methods that the compound existed in the membrane matrix when the membrane had been immersed in its aqueous solution, though the molecular weight of α-cyclodextrin is relatively high. In electrodialysis, sulfate ions, large and strongly hydrated anions, easily permeated through the membranes and nitrate ions, less hydrated anions, permeated with difficulty through the membranes in the presence of α-cyclodextrin. Because α-cyclodextrin is a hydrophilic compound, which has many ether and alcoholic groups, the hydrophilicity of the anion-exchange membranes is thought to increase. Thus, sulfate ions easily permeate and nitrate ions permeate with difficulty. This proves that the hydrophilicity of the anion-exchange membranes controls permselectivity between anions through the membranes. Received: 8 August 2000 Accepted: 24 October 2000     

Study on liquid crystallinity in 2,9-dialkylpentacenes

A series of semiconducting and symmetrical 2,9-dialkylpentacenes was successfully synthesized via a five-step process and their structures confirmed by ¹H NMR, IR and elemental analyses. Their liquid crystallinity was investigated by differential scanning calorimetry and polarizing optical microscopy. The introduction of alkyl chains also improved their solubility. For alkyl chains longer than butyl, focal conic or baton texture was observed, indicating the existence of an ordered smectic phase. Thermal analyses revealed that the both melting and smectic-isotropic transition temperatures show an odd-even effect when the alkyl chain is larger than heptyl or octyl. The synthesized compounds are promising candidates for semiconductors in organic field-effect transistors because their liquid crystallinity allows easy molecular alignment in the device fabrication process.     

Infrared thermographic analysis on copolymerization of spiroorthoester with oxetane

Infrared (IR) thermography was employed to monitor temperature changes during the copolymerization of a spiroorthoester monomer with an oxetane monomer initiated with a benzyl sulfonium salt. The temperature changes in the polymerizations decreased with the increase of the initial feed ratios of the spiroorthocarbonate monomer. For instance, the temperature in the copolymerization of the equimolar mixture of both of the monomers increased only ～1 °C, whereas that in the homopolymerization of the oxetane monomer increased more than 20 °C. This result indicates that the copolymerization employing spiroorthocarbonate monomers effectively suppress temperature increase, which are responsible to shrinkage during cooling. The suppression of polymerization shrinkage by spiroorthocarbonate was also confirmed by density measurement of the polymers using a gas pycnometer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1388–1393, 2007.     

Single- and multi-objective defensive location problems on a network

This paper considers a new optimal location problem, called defensive location problem (DLP). In the DLPs, a decision maker locates defensive facilities in order to prevent her/his enemies from reaching an important site, called a core; for example, “a government of a country locates self-defense bases in order to prevent her/his aggressors from reaching the capital of the country.” It is assumed that the region where the decision maker locates her/his defensive facilities is represented as a network and the core is a vertex in the network, and that the facility locater and her/his enemy are an upper and a lower level of decision maker, respectively. Then the DLPs are formulated as bilevel 0-1 programming problems to find Stackelberg solutions. In order to solve the DLPs efficiently, a solving algorithm for the DLPs based upon tabu search methods is proposed. The efficiency of the proposed solving methods is shown by applying to examples of the DLPs. Moreover, the DLPs are extended to multi-objective DLPs that the decision maker needs to defend several cores simultaneously. Such DLPs are formulated as multi-objective programming problems. In order to find a satisfying solution of the decision maker for the multi-objective DLP, an interactive fuzzy satisfying method is proposed, and the results of applying the method to examples of the multi-objective DLPs are shown.     

Release kinetics of (−)-menthol from chewing gum

The release kinetics of (−)-menthol from chewing gum was investigated using various encapsulated powder of (−)-menthol. The apparatus of flavor release of chewing gum was made with a glass container of mashing homogenizer. Flavor release behavior could be correlated with Avrami’s equation. Chewing gum containing (−)-menthol/γ-CD complex powder had longer retention of (−)-menthol compared with the β-CD complex powder and the (−)-menthol encapsulated in modified starches. The activation energies of (−)-menthol release from chewing gum were 106 kJ/mol for γ-CD complex and 74 kJ/mol for (−)-menthol/β-CD complex powder and emulsified (−)-menthol encapsulated in HI-CAP, respectively.     

Novel Reactive Polymers Containing Hemiacetal Ester and Vinyl Moieties: Synthesis and Selective Polymerization of 1‐Methoxyallyl Methacrylate Derived from Methacrylic Acid and Methoxyallene

A novel functional monomer, 1‐methoxyallyl methacrylate (MOAMA), was prepared and its polymerization behavior was investigated. The radical polymerization of MOAMA led to a polymeric network due to the participation of the allyl group in the reaction. Contrarily, anionic polymerization proceeded in a living fashion to yield linear poly(MOAMA) without gelation. Since both the network‐type and linear polymers possess hemiacetal ester and vinyl moieties, the two‐fold polymerization behavior of MOAMA represents a new pathway towards reactive polymers.     

Some More Conservation Results on the Baire Category Theorem

In this paper, we generalize a result of Brown and Simpson [1] to prove that RCA₀+Π⁰_∞‐BCT is conservative over RCA₀ with respect to the set of formulae in the form ∃!Xφ(X), where φ is arithmetical. We also consider the conservation of Π⁰_0∞‐BCT over Σ^b₁‐NIA+∇^b₁‐CA.     

Synthesis and Properties of Oligothymidylates Incorporating an Artificial Bend Motif

The uridylyl‐(3′→5′)‐thymidine dinucleotide block 14 (cUpdU), having a cyclic structure between the 2′‐hydroxy of the upstream uridine and the 5‐substituent of the downstream thymidine, was synthesized (Schemes 1 and 2). This cyclic structure is a stable mimic of the intraresidual H‐bonding found in the anticodon loop of an E. coli minor tRNA^Arg. The spectroscopic and molecular‐mechanics analyses of the cyclized dinucleotides predicted two major conformers, i.e., the turn and bent forms. The latter was expected to bend DNA oligomers when incorporated into them. This expectation was ascertained by incorporating the bent dimer motif into tetra‐, deca‐, or hexadecathymidylates by the conventional phosphoramidite method (see 18 – 20 in Scheme 4). The bending of oligonucleotides 18 – 20 was demonstrated by ³¹P‐NMR and CD spectra and gel‐electrophoretic studies. The duplex formation of these modified oligonucleotides with oligodeoxyadenylates was also studied. The decreased thermal stability of the duplexes when compared with unmodified ones indicates distorted structures of the modified duplexes. The 3D computer model of the duplexes showed a bend of ca. 30° with a `bulge‐out' at the position of an adenosine residue facing the cyclized dimer. The artificially bent DNAs might become a new tool for the study of the effect of DNA bending induced in DNA/DNA‐binding protein interactions.