Synthesis and properties of disulfonated (2-benzimidazolyl)(phenyl)methanone 5-nitro-2-pyridylhydrazone (S2BINPH) and spectrophotometric determination of trace amounts of nickel with S2BINPH

Disulfonated (2-benzimidazolyl)(phenyl)methanone 5-nitro-2-pyridylhydrazone (S₂BINPH) has been synthesized and its reactivity with metal ions investigated. A sensitive and selective spectrophotometric method for the determination of nickel with this reagent has been developed. S₂BINPH reacts with nickel(II) to form a stable 12 (metal ligand) complex with an absorption maximum at 501 nm. The complex formation is quantitative in the pH range 7.2–8.5. Beer's law is obeyed over the range 60–700 ng ml^–1 of nickel and the apparent molar absorptivity of the complex is 8.86 × 10⁴ mol^–1 1 cm^–1 at 501 nm. The proposed method was applied to the determination of nickel in a standard iron- and -steel sample with satisfactory results. Furthermore, proton dissociation constants of S₂BINPH and the overall formation constant of its nickel complex were also determined spectrophotometrically.     

Diastereoselection in 1,3-O- to -C-alkyl migration reaction of 1-alkenyl alkyl acetals catalyzed by boron trifluoride etherate

Remarkable diastereoselection, with (E)-alkenyl alkyl acetal giving selectively the erythro α-alkyl-β-alkoxyaldehyde, and (Z)-acetal leading preferentially to the threo isomer, is observed in the 1,3-O- to - C-alkyl migration reaction of 1-alkenyl alkyl acetals catalyzed by boron trifluoride etherate.     

Simple deprotection of acetal type protecting groups under neutral conditions

When acetals such as MOM ethers, MEM ethers, and THP ethers were heated in ethylene glycol or propylene glycol, solvolysis proceeded smoothly to produce alcohols in excellent yield. This reaction is a very promising method for chemoselective deprotection of acetal type protecting groups.     

Thermoresponsive properties of porous poly(N‐isopropylacrylamide) hydrogels prepared in the presence of nanosized silica particles and subsequent acid treatment

Porous poly(N‐isopropylacrylamide) hydrogels were prepared by the free‐radical polymerization of its monomer and a suitable crosslinker in the presence of spherical silica particles of different sizes (74 and 1600 nm) and by the subsequent acid extraction of silica. The yields were 81–83%, and the yields were not affected by the silica content. Scanning electron microscopy observations revealed the porous structure of the hydrogels. Porous and nonporous hydrogels showed volume phase transitions from swelling states to deswelling states at approximately 30 °C, as analyzed by the ratio of the diameter of cylinder‐shaped hydrogels to that of the glass tube used for the hydrogel preparation at the corresponding temperature. Deswelling, which was analyzed by rapid changes in the temperature of the aqueous media from 20 to 40 °C, was facilitated by decreased silica particle size and increased silica content. The deswelling rate constant of the hydrogel prepared with 74‐nm silica at 10 v/v % (silica/solvent) was more than 1500 times greater than that of conventional hydrogels. Swelling was similarly analyzed through changes in the temperature from 40 to 20 °C and was independent of the pore structure. The deswelling–swelling cycle was repeatable with reasonable reproducibility. Moreover, the mechanical strength of the porous hydrogels was significantly maintained compared with that of conventional nonporous hydrogels. This method produced thermoresponsive hydrogels of suitable mechanical strength and remarkable deswelling properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4228–4235, 2002     

Rapid and controlled deswelling of porous poly(N‐isopropylacrylamide) hydrogels prepared by the templating of interpenetrated nanoporous silica particles

Free radical polymerization of N‐isopropylacrylamide (NIPAAm) and crosslinker solutions, which were fulfilled in silica particles with an interpenetrated and nanometer‐sized porous structure (a diameter of 3 mm and mean pore sizes of 15, 30, and 50 nm), fabricated hybrids of organic hydrogels and inorganic silica. Differential scanning calorimetric analyses of the hybrids revealed that silica components affected the thermoresponsive properties of polyNIPAAm hydrogels. Porous polyNIPAAm hydrogels were prepared by the subsequent acid treatment of the hybrids to remove silica. Transmission Fourier transformed infrared spectra indicated the selective extraction of silica. Scanning electron microscopic observation of the hydrogels confirmed the porous structure. The deswelling rate of porous hydrogels was 7 times larger than that of conventional hydrogels and increased with increasing the pore size of silica used. However, the swelling was not affected by the pore formation. The thermoresponsiveness of porous polyNIPAAm hydrogels could be regulated by the pore size. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3542–3547, 2002     

Preparation and properties of polyamides containing p-terphenyl units

Novel polyamides that contained p-terphenyl units were prepared with inherent viscosities in the range of 0.4–1.7 dL/g by the polycondensation of 4,4″-dichloroformyl-p-terphenyl with aromatic diamines and 4,4″-diamino-p-terphenyl with aromatic dicarbonyl chlorides. Polyamides composed of only paraoriented phenylene units were insoluble in all solvents and showed a high degree of crystallinity. A series of polyamides that contained p-terphenyl units were more thermostable than corresponding polymers with p-phenylene or biphenylene linkages.     

Synthesis of double-armed lariat ethers with pyrene moieties at each end of two sidearms and their fluorescence properties in the presence of alkali metal and alkaline earth metal cations

Two types of double-armed lariat ether derivatives having pyrene moieties at each end of two sidearms, (3x + 1)-crown-x derivatives 1 (x = 5), 2 (x = 6), and 3 (x = 4) (type A) and 3y-crown-y derivatives, 6 (y = 5) and 7 (y = 6) (type B), were synthesized, and their complexation behavior toward alkali metal and alkaline earth metal cations was examined by fluorescence spectroscopy. Pyrene excimer emission decreased accompanied by an increase in monomer emission upon metal ion complexation. This finding is ascribed to the change of the spatial distance of two pyrene rings by movement suppression of both the crown ring and one of the two sidearms based on complexation with the metal cation. The selectivity for alkaline earth metal cations was highly dependent on the fitness of the host cavity and the guest size. Although most of the fluorophores did not respond to alkali metal cations, only trans-7a containing an 18-crown-6 ring showed K(+) selectivity.     

Rational Design of a Novel Intercalation System. Layer-Gap Control of Crystalline Coordination Polymers, {[Cu(CA)(H(2)O)(m)()](G)}(n)() (m = 2, G = 2,5-Dimethylpyrazine and Phenazine; m = 1, G = 1,2,3,4,6,7,8,9-Octahydrophenazine)

New copper(II) intercalation compounds, {[Cu(CA)(H(2)O)(2)](G)}(n)() (H(2)CA = chloranilic acid; G = 2,5-dimethylpyrazine (dmpyz) (1a and 1b) and phenazine (phz) (2)) have been synthesized and characterized. 1acrystallizes in the triclinic space group P&onemacr;, with a = 8.028(2) ?, b = 10.269(1) ?, c = 4.780(2) ?, alpha = 93.85(3) degrees, beta = 101.01(2) degrees, gamma = 90.04(3) degrees, and Z = 1. 1b crystallizes in the triclinic space group P&onemacr;, with a = 8.010(1) ?, b = 10.117(1) ?, c = 5.162(1) ?, alpha = 94.40(1) degrees, beta = 97.49(1) degrees, gamma = 112.64(1) degrees, and Z = 1. 2crystallizes in the triclinic space group P&onemacr;, with a = 8.071(1) ?, b = 11.266(1) ?, c = 4.991(1) ?, alpha = 97.80(1) degrees, beta = 99.58(1) degrees, gamma = 83.02(1) degrees, and Z = 1. For all the compounds, the crystal structures consist of one dimensional [Cu(CA)(H(2)O)(2)](m)() chains and uncoordinated guest molecules (G). Each copper atom for 1a, 1b, and 2 displays a six-coordinate geometry with the two bis-chelating CA(2)(-) anions and water molecules, providing an infinite, nearly coplanar linear chains running along the a-direction. Theses chains are linked by hydrogen bonds between the coordinated water and the oxygen atoms of CA(2)(-) on the adjacent chain, forming extended layers, which spread out along the ac-plane. The guest molecules are intercalated in between the {[Cu(CA)(H(2)O)(2)](k)()}(l)() layers, just like pillars, which are supported with N.H(2)O hydrogen bonding. The guest molecules are stacked each other with an interplanar distance of ca. 3.2 ? along the c-axis perpendicular to the [Cu(CA)(H(2)O)(2)](m)() chain. The EHMO band calculations of intercalated dmpyz and phz columns show an appreciable band dispersion of phz pi (b(2g) and b(3g)) and dmpyz pi (b(g)), indicative of the importance of planar pi structure for the formation of the intercalated structure. The distances of O-H---N (guest molecules) fall within the range 2.74-2.80 ?, insensitive to the guest, whereas the interlayer distances increase in the order 9.25 ? (1b), 10.24 ? (1a), and 11.03 ? (2). The degree in lengthening the distance correlates well with the size of a molecule, indicative of the stability of the 2-D sheet structure and the flexibility of the sheet packing. The magnetic susceptibilities were measured from 2 to 300 K and analyzed by a one-dimensional Heisenberg-exchange model to yield J = -1.83 cm(-)(1), g = 2.18 (1a), J = -0.39 cm(-)(1), g = 2.14 (1b), and J = -1.84 cm(-)(1), g = 2.18 (2). The absolute value of J is smaller than that value for [Cu(CA)](n)(), which has a planar ribbon structure suggesting that the magnetic orbital d(x)()()2(-)(y)()()2 is not parallel to the chloranilate plane. For comparison with phz another type of copper(II) coordination compound, {[Cu(CA)(H(2)O)](ohphz)}(n)() (ohphz = 1,2,3,4,6,7,8,9-octahydrophenazine (7)) has also been obtained. 7 crystallizes in the orthorhombic space group Cmcm with a = 7.601(2) ?, b = 13.884(2) ?, c = 17.676(4) ?, and Z = 4. Nonplanar ohphz molecules are in between [Cu(CA)(H(2)O)(2)](m)() chains with the N.H(2)O hydrogen bonding in a fashion parallel to the chain direction. The copper atom shows a five-coordinate square-pyramidal configuration with two CA and one water molecule, thus affording no hydrogen bonding links between chains, dissimilar to 1a, 1b, and 2. The magnetic susceptibilities yield J = -10.93 cm(-)(1) and g = 2.00, comparable to that of the four-coordinate [Cu(CA)](n)(). On this basis both hydrogen bonding and stack capability of a guest molecule is responsible for building the unique intercalated structure such as is seen in 1a, 1b, and 2.     

Lipid carrier systems for targeted drug and gene delivery

For effective chemotherapy, it is necessary to deliver therapeutic agents selectively to their target sites, since most drugs are associated with both beneficial effects and side effects. The use of lipid dispersion carrier systems, such as lipid emulsions and liposomes, as carriers of lipophilic drugs has attracted particular interest. A drug delivery system can be defined as a methodology for manipulating drug distribution in the body. Since drug distribution depends on the carrier, administration route, particle size of the carrier, lipid composition of the carrier, electric charge of the carrier and ligand density of the targeting carrier, these factors must be optimized. Recently, the lipid carrier system has also been applied to gene delivery systems for gene therapy. However, in both drug and gene medicine cases, a lack of cell-selectivity limits the wide application of this kind of drug and/or gene therapy. Therefore, lipid carrier systems for targeted drug and gene delivery must be developed for the rational therapy. In this review, we shall focus on the progress of research into lipid carrier systems for drug and gene delivery following systemic or local injection.     

Synthesis of polyamides by direct polycondensation with (1,2-benzisoxazol-3-yl) diphenyl phosphate as a new activating agent

A new activating agent for amide condensations, (1,2-benzisoxazol-3-yl) diphenyl phosphate ( 1 ), was readily prepared in high yield by the reaction of 1,2-benzisoxazol-3-ol ( 2 ) with diphenyl phosphorochloridate ( 3 ) in the presence of triethylamine in benzene. The new activating agent 1 was found to be very useful for the preparation of amides from carboxylic acids and amines. The direct polycondensation of several dicarboxylic acids with aromatic diamines using the activating agent 1 in the presence of triethylamine proceeded slowly at room temperature to produce polyamides with inherent viscosities up to 1.2 dL g^?1.