Preparation of Building Blocks for Carba‐Oligosaccharides: Some Protected 5a′‐Carba‐D‐hexopyranosyl‐1,5‐anhydro‐2‐deoxy‐D‐arabino‐hex‐1‐enitols,and 5a,5a′‐Dicarba Congeners Thereof

Four configurational types of two protected O‐linked (5a‐carba‐D‐hexopyranosyl)‐D‐glucal and carba‐D‐glucal derivatives were prepared in order to provide versatile synthetic intermediates readily convertible into carba‐oligosaccharides of biological interest. These compounds may also find application as donors for elongation of carba‐oligosaccharide chains having O‐linked carbahexopyranose residues at nonreducing ends.     

Synthesis and Sweetness of Pseddo-β-D and L-Frdctopyranose

Abstract

Pseudo-β-D (D-2) and L-fructopyranose (L-2), 1(S) and (1R)-(1,2/-3,4)-4-C-hydroxymethyl-1,2,3,4-cyclohexanetetrol, have been synthesized, starting from optically active endo-adducts of furan and acrylic acid, following the modified procedure used for the preparation of the racemic modification. It has been demonstrated that the D and L-enantiomers are nearly as sweet as D-fructose, and the former is somewhat sweeter than the latter.     

Intramolecular Radical,Knoevenagel, or SN2′ Cyclization of Carbohydrate Derivatives for Access to Enantiomerically Pure 2-Oxospiroalkanes

Abstract

Intramolecular radical cyclization of D-glucose-derived substrate, (2R,3R,4R,5S)-2, 3-(isopropylidenedioxy)-5-[(1R)-l, 2-(isopropylidenedioxy)ethyl]-4-[3-bromo-3, 3-bis(methoxycarbonyl)propyl]-4-vinyltetrahydrofuran, 7 proceeded in a 6-endo-trig mode to give a derivative of 2-oxaspiro[4.5]decane 8 exclusively. Intramolecular Knoevenagel-like reaction of substrate 9 afforded derivatives of 2-oxaspiro-[4.4]nonane 10 as a 3:1 diastereomeric mixture. Intramolecular SN²′ displacement of substrate 22 proceeded highly stereoselectively giving a derivative of 2-oxaspiro-[4.4]decane 23.     

Ideal spread monolayer and multilayer formation of fully hydrophobic polythiophenes via liquid crystal hybridization on water

The spread monolayer formation of hydrophobic poly(3-alkylthiophene)s (P3ATs), regioregular poly(3-hexylthiophene) ( HT-P3HT), regioregular poly(3-dodecylthiophene) ( HT-P3DT), and regioirregular poly(3-hexylthiophene) ( RI-P3HT), were attained on the water surface via cospreading with a liquid-crystal molecule, 4'-pentyl-4-cyanobiphenyl (5CB). The spread monolayers were characterized by pi- A isotherms, Brewster angle microscopy (BAM), and atomic force microscopy (AFM). The molecular area for the cospread mixtures of P3ATs and 5CB expanded more than that of pure P3ATs as shown from the pi-A isotherms. BAM revealed that the mixed film forms the monomolecularly uniform and flat films on water. AFM elucidated that the spread monolayer of the hydrophobic P3ATs formed on the top of the 5CB monolayer on water with thicknesses of ca. 1.6 and ca. 2.6 nm for the two P3HTs and HT-P3DT, respectively. The P3AT/5CB hybrid monolayers could be fully transferred onto a solid substrate, and pure P3AT monolayers were obtained after volatilization of 5CB by gentle heating. The multilayer formation of pure P3AT monolayers was prepared by layer-by-layer deposition involving repeating horizontal deposition and successive volatilization of 5CB. Grazing angle incidence X-ray diffraction measurements showed that the lamella plane of the P3ATs is perfectly oriented parallel to the substrate plane in the resulting thin films. This shows a marked contrast with those obtained by spin casting using the identical polymer, where both in-plane and out-of-plane lamellae are involved. These thin films with perfectly controlled lamella orientation should be of great significance as the model system for evaluating the charge mobility for organic polymer electric devices.     

Enhancement of ordinal CoMFA by ridge logistic partial least squares

Conventional comparative molecular field analysis (CoMFA) requires at least 3 orders of experimental data, such as IC 50 and K i, to obtain a good model, although practically there are many screening assays where biological activity is measured only by rating scale. To improve three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis, we developed in this study a modified ordinal classification-oriented CoMFA using partial-least-squares generalized linear regression and ridge estimation. The modified Logistic CoMFA was validated using a corticosteroid binding globulin receptor binding data set, a benchmark for 3D-QSAR, and an acetylcholine esterase inhibitor data set. Our results show that modification of Logistic CoMFA enhanced both prediction accuracy and 3D graphical analysis. In addition, the 3D graphical analysis of the modified Logistic CoMFA was much improved. This improvement resulted in more accurate information on the binding mode between proteins and ligands than in the case of conventional CoMFA.     

Photoinduced electron transfer of N-[(3- and 4-diarylamino)phenyl]-1,8-naphthalimide dyads: orbital-orthogonal approach in a short-linked D-A system

The photoinduced electron transfer of a series of meta- and para-linked triphenylamine-naphthalimide dyads, N-{3- and 4-[bis(4-R-substituted phenyl)amino]phenyl}-1,8-naphthalimide, 1m,p (R = H), 2m,p (R = Me), 3m,p (R = OMe), and 4m,p (R = NMe2) was investigated in toluene and DMF. The singlet charge-transfer (CT) states were observed in all cases. The decay rates were found to be faster in DMF (tau = 6.5 ps to 100 ps) than those in toluene (tau = 190 ps to 7 ns). The long-lived triplet CT states were observed in toluene for 3 (ca. 10% contribution, tau = 670 ns for 3m, 240 ns for 3p). No long-lived species were detected in DMF. The decay rates were somewhat faster in the para-isomers than in the meta-isomers in most cases. The photolysis of 5 (p-phenylene extended analogue of 3, R = OMe) gave a singlet CT state and a locally excited triplet state on the naphthalimide chromophore.     

Preparation of a cellulose-based enzyme membrane using ionic liquid to lengthen the duration of enzyme stability

A novel method for preparing enzyme membranes was developed. The enzyme was attached onto the electrode surface by dropping the enzyme solution and allowing it to dry. Glucose oxidase was used for entrapment. Then, the electrode surface was coated with an ionic liquid containing cellulose, and the ionic liquid was removed by immersing the electrode into water. Enzyme activity was retained in the membrane; the enzyme electrode can be used for detecting glucose in the range of 10 μM to 1 mM, and the response time was ~10 s. The stability duration of the electrode was examined: the enzyme electrode could be used for glucose detection for 6 months. The membrane was observed by atomic force microscopy in the force modulation mode; crystalline and amorphous parts were intermingled. In conclusion, the cellulose membrane can be a suitable immobilization matrix for enzymes.     

Metallization of a genetically engineered polypeptide

Recently, well-ordered biological materials have been exploited to pattern inorganic nanoparticles into linear arrays that are of particular interest for nanoelectronic applications. In this work, a de novo designed E. coli-expressed polypeptide (previously shown to form highly rectilinear, β-sheet-containing structures) operates as a template for divalent metal cations. EDX and TEM analysis verify the attachment of platinum ions to the histidine-rich fibril surface, which was designed specifically to facilitate attachment of chemical moieties. Following chemical reduction, TEM further confirms the formation of localized zero-valent metal aggregates with sub-nanometer interparticle spacing.     

Design of a multinuclear Zn(II) complex as a new molecular probe for fluorescence imaging of His-tag fused proteins

A Zn(II) complex (Zn(II)-Ida) was designed as the new fluorescent probe for His-tag fused proteins. Thanks to the tight binding ability to histidine-rich sequences and bright fluorescence property of the Cy5-appended Zn(II)-Ida probes, selective and clear fluorescent imaging of the His-tag fused G-protein coupled receptors on live cell surfaces was carried out.     

Soft-x-ray harmonic comb from relativistic electron spikes

We demonstrate a new high-order harmonic generation mechanism reaching the "water window" spectral region in experiments with multiterawatt femtosecond lasers irradiating gas jets. A few hundred harmonic orders are resolved, giving μJ/sr pulses. Harmonics are collectively emitted by an oscillating electron spike formed at the joint of the boundaries of a cavity and bow wave created by a relativistically self-focusing laser in underdense plasma. The spike sharpness and stability are explained by catastrophe theory. The mechanism is corroborated by particle-in-cell simulations.