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     

Synthesis of the Carbon Framework of Scholarisine A by Intramolecular Oxidative Coupling

Scholarisine A, isolated from the leaves of Alstonia scholaris, is a monoterpene indole alkaloid with an unprecedented cage‐like structure. In this paper, preparation of the distinctive cage‐like core skeleton of scholarisine A is described. The key feature of this synthetic strategy is an intramolecular oxidative coupling reaction at the late stage to construct a 10‐oxa‐tricyclo[5.3.1.0^{3, 8}]undecan‐9‐one structure fused with indolenine. Intramolecular oxidative coupling by using N‐iodosuccinimide gave the carbon framework of scholarisine A in moderate yield, which is the first example of intramolecular oxidative‐coupling reaction between non‐activated enolate and indole. This study lays the foundation for continued investigations towards the total synthesis of scholarisine A.