3′-Amino-5′-carboxymethyl-3′,5′-dideoxy nucleosides for the synthesis of fully amide-linked RNA mimics

A convenient protocol is developed for the synthesis of 3′-[N-(fluorenylmethoxycarbonyl)-amino]-5′-carboxymethyl derivatives of all four natural ribonucleosides from cheap chiral pool compound glucose. Synthesis of fully amide-linked RNA analogues of small oligonucleotides containing, for the first time, all four nucleoside amino acids using standard solid phase Fmoc-chemistry is described.     

Amino- and hydroxy-functionalized 11-azaartemisinins and their derivatives

An efficient conversion of artemisinin 1 into three new amino- and hydroxy-functionalized 11-aza prototypes 9, 11, and 12 has been achieved on a multigram scale by reaction with hydrazine, hydroxylamine, and 2-amino ethanol, respectively. Of these, 9 has been further diversified into a wide range of derivatives including imines, amines, amides, and linker based dimers. Prototypes 11 and 12 have been converted into the corresponding ethers in high yields. Some of these compounds have shown a high order of activity against multidrug-resistant malaria in mice by oral route.     

Chemical composition and antimicrobial activity of the inflorescence essential oil of Capillipedium parviflorum (R. Br.) Stapf. from India

Essential oil isolated from the inflorescences of Capillipedium parviflorum (R. Br.) Stapf., collected from Kumaon region of Western Himalaya, India, was investigated by GC and GC-MS. A total of 45 constituents representing 99.0% of the essential oil were identified. The major components of this oil were 4-undecanone (33.2%), 4-undecanol (29.7%), 4-nonanol (13.9%), α-muurolol (5.3%), 4-tridecanone (3.6%), methyl-2-oxo-nonanoate (3.1%), trans-2-hexenyl butanoate (1.1%) and 1-tetradecanol (1.0%). The antimicrobial activity of the essential oil was determined against eight Gram-positive and Gram-negative bacterial strains, as well as two fungal strains. The bioassay showed that the essential oil possessed good antibacterial activity.     

Structural and magnetic studies on copper(II) azido complexes

The azide ligand has been receiving intense attention in the rapid growth of literature in the field of molecular magnetism. Primarily, azide ion functions as a bridging ligand and magnetic coupler of paramagnetic metal ions. This review is centered on the study of diverse structural and magnetic properties of copper(II) azido complexes. Some of the trends identified could serve as a privileged starting point for the further development of this promising area.     

A highly efficient and recyclable silica-supported palladium catalyst for alcohol oxidation reaction

A silica supported palladium catalyst (SiO₂@APTES-Pd) showed excellent activity and reusability for selective oxidation of alcohols to corresponding carbonyl compounds with H₂O₂ as oxidant under base free environment. A wide range of alcohols including aliphatic alcohols are tolerated as substrates with a low loading of palladium (0.1 mol %).     

Spatial Structuring of a Supramolecular Hydrogel by using a Visible‐Light Triggered Catalyst

Spatial control over the self‐assembly of synthetic molecular fibers through the use of light‐switchable catalysts can lead to the controlled formation of micropatterns made up of hydrogel structures. A photochromic switch, capable of reversibly releasing a proton upon irradiation, can act as a catalyst for in situ chemical bond formation between otherwise soluble building blocks, thereby leading to fiber formation and gelation in water. The use of a photoswitchable catalyst allows control over the distribution as well as the mechanical properties of the hydrogel material. By using homemade photomasks, spatially structured hydrogels were formed starting from bulk solutions of small molecule gelator precursors through light‐triggered local catalyst activation.     

Effect of Na‐ionomer on dynamic rheological,dynamic mechanical and creep properties of acrylonitrile styrene acrylate (ASA)/Na+1 poly (ethylene‐co‐methacrylic acid) ionomer blend

A special class of engineered copolymers, called ionomers, comprising both electrically neutral repeating units and a fraction of ionized units was melt blended to weather resistant acrylonitrile/styrene/acrylate (ASA) terpolymer for improved electrical conductivity, heat sealing ability, direct adhesion to several polymers, glass and metals without affecting the aesthetics and colorability of ASA. The similar chemical nature of one of the components of each blended materials viz. acrylate rubber in ASA and acrylic acid of Na‐ionomer in addition to the presence of ionic crosslinking within Na‐ionomer, polar acrylonitrile group in ASA affects chain dynamics as compared to neat polymers. In this context, dynamic rheological properties, DMA properties, creep behavior and DSC of the newly developed ASA/Na‐ionomer blends were analyzed. Based on Na‐ionomer content, the blend system either forms “mushroom” or “brush” type conformation and formation of ionic crosslinking in “brush regime” leads to three tiers Caylay tree conformation. The different chain topology resulted into characteristic loss modulous (G″) curve during stress relaxation process. The chain conformation as well as ionic crosslinking and ion–dipole interaction between the blend components also affected DSC endotherm peak and glass transition temperature. The tan δ peak temperature from DMA also revealed the similar observation. The creep compliance of the blends was dependent on Na‐ionomer content and with temperature. The Findley model analysis of creep compliance suggested that the creep compliance was depended on Na‐ionomer content and ionic crosslinking controlled the creep. The findings can be utilized to design weather resistant smart polymer using suitable filler system. Copyright © 2014 John Wiley & Sons, Ltd.     

POM‐Catalyzed In Situ Ligand Synthesis for the Construction of Metal Complexes and Their Use in the Formation of Coordination Polymers

Six organic–inorganic hybrid materials were synthesized by the in situ oxidation of neocuproine by using MoO₃/Na₂MoO₄ as the catalyst in the presence of Cu(NO₃)₂. The crystal structures of Mo8‐Cu4‐PHEN and Mo8‐Cu2‐5(2PIC) are composed of [Mo₈O₂₆]^4? polyoxometalate (POM) units, whereas the crystal structure of Mo6‐Cu‐COPHEN is composed of a [Mo₆O₁₉]^2? POM unit; both POM units could be considered as the active form of the catalyst. Reaction of the hybrid materials with 1,3,5‐benzenetricarboxylic acid (BTC) resulted in the formation of two different coordination polymers (CPs) under different reaction conditions. These CPs, depending on their structural attributes, exhibit distinct differences in the adsorption of H₂, CO₂, and water. The use of 2‐methylpyridine instead of neocuproine does not give any oxidation products under the same reaction conditions due to the incorrect positioning of the methyl group with respect to the Cu^II center.     

Bio-inspired Design of Bidirectional Oxygen Reduction and Oxygen Evolution Reaction Molecular Electrocatalysts

The proper utilization of renewable energy sources has emerged as a major challenge in our pursuit of a sustainable and carbon-neutral energy landscape. Small molecule activation is a key component for proper utilization of renewable energy resources, where O₂/H₂O redox couple is reckoned to be a potential game changer. In this regard, electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have become the prime interest of catalyst designers. Typically, these ORR and OER electrocatalysts are developed distinctly; however, very soon, the requirement of a bidirectional ORR/OER electrocatalyst becomes obvious for practical applicability and rapid energy transduction purposes. A bidirectional catalyst is defined as a catalyst capable of driving a redox reaction in opposing directions. This review has portrayed the development of enzyme structure-inspired design of molecular bidirectional ORR/OER catalysts. The strategic incorporation of secondary and outer coordination sphere features has significantly enhanced the performance of these catalysts, which can be monitored via the key catalytic parameters. These bifunctional OER/ORR catalysts are vital for metal-air battery and fuel cell applications and appropriately poised to lay the foundation for an efficient, economical, and eco-friendly pathway for sustainable energy usage with the rational assembly of energy converting and storage devices.