Enzymatic synthesis of cellulose in space: gravity is a crucial factor for building cellulose II gel structure

Cellulose - We previously reported in vitro synthesis of highly ordered crystalline cellulose II by reverse reaction of cellodextrin phosphorylase from the cellulolytic bacterium Clostridium...     

Preparation of renieramycin left-half model compounds

Model compounds of the left-half of renieramycins, which are anticancer marine natural products having an α-aminonitrile functionality, were prepared from phenylalanine derivatives. The key step of the transformation is the stereospecific construction of 1,3-cis stereochemistry via an exomethylene intermediate. The stereoselective α-aminonitrile formation under kinetically controlled conditions is also discussed. The initial cytotoxicity profiles are presented.     

Variability of 40K isotopic composition in forest soils under different environmental conditions

Radiopotassium isotopic composition (⁴⁰K/K, %) of several forest soils did not show a constant value of generally known 1.17 × 10^?2 %, but they were varied significantly from 0.4 × 10^?2 to 1.3 × 10^?2 % at different locations under different environmental conditions. Surface portion of a soil (2–4 cm in depth) gave always lower ⁴⁰K/K values compared with those of deeper soil layer (35–40 cm in depth). Ion exchange of K⁺ with NH₄ ⁺ did not affects the ⁴⁰K/K value in any soils, which revealed with chemical leaching experiments in the laboratory. Some plant species showed much lower ⁴⁰K/K values than those in the surface soil. Possible reasons for varying ⁴⁰K/K values obtained in this study may result from a dynamic behavior of potassium in soil, probably due to biological activity including root uptake and decomposing soil organic matter by microorganisms in the forest floor.     

Merging Pd0/PdII Redox and PdII/PdII Non-redox Catalytic Cycles for the Allylarylation of Electron-Deficient Alkenes

An allylarylation of electron-deficient alkenes with aryl boronates and allylic carbonates has been developed. This method allows access to a wide variety of carbon skeletons from readily available starting materials. Mechanistic studies indicate that this reaction is enabled by a cooperative catalysis based on merging Pd⁰/Pd^II redox and Pd^II/Pd^II non-redox catalytic cycles.     

Polymerization of an epoxy‐containing silacyclobutane and its application to networked polymer synthesis

Polymerization of a silacyclobutane having an epoxy moiety and its application to networked polymer synthesis were examined. Four‐membered ring‐opening polymerization of silacyclobutane having a 3,4‐epoxybutyl group on the silicon atom (OBMSB) was achieved by using a platinum vinyldisiloxane complex with keeping the epoxy ring unchanged. Copolymerization of 1,1‐diethylsilacyclobutane (DESB) with OBMSB by using the same catalyst effectively gave the corresponding copolymers [poly(DESB‐co‐OBMSB)]. Thermal properties of the polyOBMSB, polyDESB, and poly(DESB‐co‐OBMSB) were investigated by DSC and TGA. Cast films of the obtained polymers with 1‐naphthylmethylmethyl‐p‐hydroxyphenylsulfonium hexafluoroantimonate, a small amount of thermally latent acid generator were prepared. Heating the films at 80 °C for 2 h gave crosslinked networked polycarbosilanes through cationic ring‐opening of the epoxy moieties. Thermal and mechanical properties of the networked polymers were investigated by TGA, DSC, and tensile strength measurements. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3400–3405     

Supramolecular Interaction of Fullerenes with a Curved π‐Surface of a Monomeric Quadruply Ring‐Fused Porphyrin

Molecular binding of fullerenes, C₆₀ and C₇₀, with the Zn^II complex of a monomeric ring‐fused porphyrin derivative ( 2 ‐py) as a host molecule, which has a concave π‐conjugated surface, has been confirmed spectroscopically. The structures of associated complexes composed of fullerenes and 2 ‐py were explicitly established by X‐ray diffraction analysis. The fullerenes in the 2:1 complexes, which consist of two 2 ‐py molecules and one fullerene molecule, are fully covered by the concave surfaces of the two 2 ‐py molecules in the crystal structure. In contrast, in the crystal structure of the 1:1 complex consisting of one 2 ‐py molecule and one C₆₀ molecule, the C₆₀ molecule formed a π–π stacked pair with a C₆₀ molecule in the neighboring complex using a partial surface, which was uncovered by the 2 ‐py molecule. Additionally, the molecular size of fullerene adopted significantly affects the ¹H NMR spectral changes and the redox properties of 2 ‐py upon the molecular binding.