Radical copolymerization of 3-tri-n-butylstannylstyrene with several vinyl monomers

The free radical homopolymerization and copolymerization of 3-tri-n-butylstannylstyrene (3-BTS) with styrene (ST), ethyl acrylate (EA), methyl methacrylate (MMA), vinyl acetate (VA), and acrylonitrile (AN) were carried out using 2,2′-azobisisobutyronitrile (AIBN) at 60°C. It was found that the yield of conversion to poly(3-BTS) increased with the molar ratio of initiator to monomer as well as with polymerization time. The conversion at equilibrium after 50 h was about 40%. The compositions of copolymer samples were determined from elemental analyses. Monomer reactivity ratio and Q-e values were calculated. The copolymers of 3-BTS-MMA and 3-BTS-AN were found to be alternating. The copolymers of 3-BTS with MMA, EA and AN were not soluble in any of a large number of organic solvents tested. The insolubility is believed to be due to formation of intermolecular coordination among the tributylstannyl moiety and the carbonyl or cyano groups of the polymer. These copolymers, however, were “soluble” in trihaloacetic acid, but this solubility was due to a cleavage of the trialkyltin moiety from the phenyl groups. The glass temperatures, T_g, and melting temperatures T_m, of the various polymers were also studied.     

Ring transformation reactions of C-nucleosides: Facile synthesis of pyrazolo[1,5-a]pyrimidine and pyrazolo[1,5-a]triazine C-nucleosides

1,3-Dimethyluracil ( 1 ), a versatile synthon for the synthesis of various heterocycles, reacted readily with 3-aminopyrazoles 2 in sodium ethoxide to give pyrazolo[1,5-a]pyrimidines 3 . Under similar conditions, 3-aminopyrazole C-nucleosides 4 and the synthon 1 gave a mixture of pyrazolo[1,5-a]pyrimidine C-nucleosides, which was separated on a silica gel column. Attempts to remove the protecting groups yielded pyranose derivative 10 . Another synthon 1,3-dimethyl-5-azauracil and 3-aminopyrazoles 12 gave pyrazolo[1,5-a]triazines 13 . In a similar reaction with 3-aminopyrazole C-nucleosides 4 gave the corresponding pyrazolo[1,5-a]-triazine C-nucleosides 14 and 15 .     

In vivo magnetic resonance detection of cancer by using multifunctional magnetic nanocrystals

The unique properties of magnetic nanocrystals provide them with high potential as key probes and vectors in the next generation of biomedical applications. Although superparamagnetic iron oxide nanocrystals have been extensively studied as excellent magnetic resonance imaging (MRI) probes for various cell trafficking, gene expression, and cancer diagnosis, further development of in vivo MRI applications has been very limited. Here, we describe in vivo diagnosis of cancer, utilizing a well-defined magnetic nanocrystal probe system with multiple capabilities, such as small size, strong magnetism, high biocompatibility, and the possession of active functionality for desired receptors. Our magnetic nanocrystals are conjugated to a cancer-targeting antibody, Herceptin, and subsequent utilization of these conjugates as MRI probes has been successfully demonstrated for the monitoring of in vivo selective targeting events of human cancer cells implanted in live mice. Further conjugation of these nanocrystal probes with fluorescent dye-labeled antibodies enables both in vitro and ex vivo optical detection of cancer as well as in vivo MRI, which are potentially applicable for an advanced multimodal detection system. Our study finds that high performance in vivo MR diagnosis of cancer is achievable by utilizing improved and multifunctional material properties of iron oxide nanocrystal probes.     

A metal-organic bilayer open framework with a dynamic component: single-crystal-to-single-crystal transformations

A metal-organic bilayered open framework, [Ni2(C26H52N10)]3[BTC]4.6C5H5N.36H2O (BOF-1, 1), has been prepared by the self-assembly of a new bismacrocyclic nickel(II) complex [Ni2(C26H52N10)(Cl)4].H2O (A) and sodium 1,3,5-benzenetricarboxylate (Na3BTC) in the mixture of water/DMSO/pyridine. The X-ray crystal structure of 1 shows that 2D layers with the cavities of brick-wall motifs (22.6 x 14.3 A2) are formed by the coordination of the nickel(II) complex with BTC3- ions and that the two 2D layers are linked with the p-xylyl bridging groups of the bismacrocycles as pillars to generate 3D channels in the bilayered framework. The voids of the channels occupy 61% of the total volume, which are filled with pyridine and water guest molecules. When 1 was dried at 75 degrees C for 1.5 h, [Ni2(C26H52N10)]3[BTC]4.4H2O (2) resulted by maintaining the single-crystallinity, which exhibited a dramatic decrease in the interlayer spacing as well as changes in the cell parameters. Solid 2 differentiates various alcohols such as MeOH, EtOH, isopropyl alcohol, and benzyl alcohol in toluene. When 1 was immersed in insoluble solvents such as pyridine and benzene, some guest molecules were exchanged with the aromatic molecules to give [Ni2(C26H52N10)]3[BTC]4.20pyridine.6H2O (3) and [Ni2(C26H52N10)]3[BTC]4.14benzene.19H2O (4), respectively. The guest-exchange processes also involve single-crystal-to-single-crystal transformation.     

Vitamin D side chain triazole analogs via cycloaddition `click' chemistry

Cycloaddition of a vitamin D side chain terminal acetylene with phenyl azide and separately with a vitamin D side chain terminal azide produced the corresponding 1,2,3-triazole monomeric and dimeric analogs of 1α-hydroxyvitamin D₃ in good yields.     

Investigation of the scanning tunneling microscopy image, the stacking pattern, and the bias-voltage-dependent structural instability of 1,10'-phenanthroline molecules adsorbed on Au(111) in terms of electronic structure calculations

A self-assembled monolayer of 1,10'-phenanthroline (phen) molecules on Au(111) was found to undergo a structural phase transition when the bias voltage is switched in scanning tunneling microscopy (STM) experiments (Phys. Rev. Lett. 1995, 75, 2376; Surf. Sci. 1997, 389, 19). The nature of two bright spots representing each phen molecule in the high-resolution STM images of phen molecules on Au(111) was identified by calculating the partial density plots for a monolayer of phen molecules adsorbed on Au(111) with tight-binding electronic structure calculations. The stacking pattern of chains of phen molecules on Au(111) was explained by studying the intermolecular interactions between phen molecules on the basis of first-principles electronic structure calculations for a phen dimer, (phen)(2). The structural instability of phen molecule arrangement caused by the bias-voltage switch was probed by estimating the adsorbate-surface interaction energy with the point-charge approximation for Au(111).     

A hybrid consisting of coordination polymer and noncovalent organic networks: a highly ordered 2-D phenol network assembled by edge-to-face pi-pi interactions

A 2-D metal-organic open framework having 1-D channels, [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).18H(2)O (1), was constructed by the self-assembly of the Cu(II) complex of hexaazamacrocycle A (A = C(10)H(26)N(6)) with sodium 1,3,5-benzenetricarboxylate (BTC(3)(-)) in DMSO-H(2)O solution. 1 crystallizes in the trigonal space group P with a = b = 17.705(1) A, c = 6.940(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 1884.0(3) A(3), Z = 1, and rho(calcd) = 1.428 g cm(-3). The X-ray crystal structure of 1 indicates that each Cu(II) macrocyclic unit binds two BTC(3-) ions in a trans position and each BTC(3-) ion coordinates three Cu(II) macrocyclic complexes to form 2-D coordination polymer layers with honeycomb cavities (effective size 8.1 A), and the layers are packed to generate 1-D channels perpendicularly to the 2-D layers. Solid 1 binds guest molecules such as MeOH, EtOH, and PhOH with different binding constant and capacity. By the treatment of 1 with aqueous solution of phenol, a hybrid solid [Cu(C(10)H(26)N(6))](3)[C(6)H(3)(COO)(3)](2).9PhOH.6H(2)O (2) was assembled. 2 crystallizes in the trigonal R3 space group with a = b = 20.461(1) A, c = 24.159(1) A, alpha = beta = 90 degrees, gamma = 120 degrees, V = 8759.2(7) A(3), Z = 3, and rho(calcd) = 1.280 g cm(-3). In 2, highly ordered 2-D noncovalent phenol layers are formed by the edge-to-face pi-pi interactions between the phenol molecules and are alternately packed with the coordination polymer layers in the crystal lattice.     

Reaction monitoring of succinylation of collagen with matrix-assisted laser desorption/ionization mass spectrometry

Succinylated collagen was synthesized by the reaction of collagen with succinic anhydride under basic conditions for one hour. Using the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) technique, the reaction products were directly identified without multi-step separation processes. MALDI-MS monitored the reaction more accurately than the conventional method of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). From the change in molecular mass during the reaction, it is observed that about 28 succinyl groups are attached to the collagen strand.