Carbocyclic Ring Closure of Aryl C-Glycosides Promoted by Fluoroboric Acid.

A novel transformation from rhamnose-type C-glycosides to 2-cyclopentenones is described. With the promotion of fluoroboric acid, C-glycosides underwent ring opening and subsequent Nazarov cyclization to afford 2-cyclopentenones in good to excellent yields. The solvent and the concentration of acid are crucial to the yield of this transformation.

Effectiveness of Amygdalus mongolica oil in hyperlipidemic rats and underlying antioxidant processes.

The seeds of Amygdalus mongolica contain various constituents including flavonoids and vitamin E, which are known to exert antioxidant effects. However, the safety of the oil extract of this compound is not fully known. The aim of this study was to determine the physicochemical properties of A. mongolica oil, identify the constituents and subsequently assess the effectiveness of utilizing this seed extract in hyperlipidemia as an antioxidant agent. In particular, the toxicity and safety of A. mongolica oil were examined with emphasis on effects on blood lipids level and serum lipid peroxidation using a hyperlipidemia rat model. Treatment with 20 ml/kg A. mongolica oil produced no apparent adverse effects after 14 days in normal female and male rats. A dose of 2.5-10 ml/kg A. mongolica oil administered to hyperlipidemic male rats significantly decreased serum total cholesterol (TC), low-density lipoprotein-C (LDL-C), malondialdehyde (MDA), total cholesterol high-density lipoprotein-C (TC/HDL-C), LDL-C/HDL-C, and atherosclerosis index(AI). In contrast, glutathione (GSH) levels and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were significantly increased. Data demonstrated that A. mongolica oil may be utilized in conditions of hyperlipidemia due to its antioxidant effects.

Lignin-derivable block copolymer micelle for effectively reinforcing and toughening polylactic acid.

The development of high-performance biodegradable polylactic acid (PLA) materials integrating high strength, malleability and toughness is desired but an ongoing challenge. In this work, a novel full-biobased block copolymer was designed and synthesized by grafting L (+)-lactide (L-LA) and ε-caprolactone (ε-CL) onto lignin via ring-opening polymerization. The obtained lignin-PLA-PCL block copolymer was composed of rigid lignin and poly (LA-CL) rubber segment, could self-assemble into uniform nano-micelles with average diameters of 80-100 nm regulated by simply altering copolymer content. The incorporation of lignin-PLA-PCL copolymers into PLA matrix induced the formation of many cavities, promoted free volume between PLA matrix and copolymer to accelerate chain mobility, achieving excellent ductility and stretchability with maximum stretching deformation of 64.8 %. The resultant PLA composites with the copolymer content as low as 5 wt% displayed simultaneously improved strength (41.84 MPa) and toughness (8.1 MJ/m3), 6.7 % and 1520 % increment than those of neat PLA, respectively. The reinforcing and toughening mechanisms were explored and verified that the combination of cavity growth and fibrillation, followed by extensive shear yielding of matrix, causing substantial plastic deformation. This study extended the design strategy and the foundation for simultaneous reinforcing and toughening PLA plastics using lignin-derived rubbery micelles.

Strong and flexible lignocellulosic film fabricated via a feasible molecular remodeling strategy.

Biomass-derived sustainable film is a promising alternative to synthetic plastic, but hampered by strength, toughness and flexibility trade-off predicament. Here, a feasible and scalable strategy was proposed to fabricate strong and flexible lignocellulosic film through molecular reconstruction of cellulose and lignin. In this strategy, polyphenol lignin was absorbed and wrapped on the surface of cellulose fiber, forming strong interfacial adhesion and cohesion via intramolecular and intermolecular hydrogen bonding. Further, covalent ether bond was generated between the hydroxyl groups of lignocellulose to form chemical cross-linking network induced by epichlorohydrin (ECH). The synergistic effect of hydrogen bonding and stable chemical cross-linking enabled the resultant lignocellulosic film (ELCF) with outstanding mechanical strength of 132.48 MPa, the elongation at break of 9.77 %, and toughness of 9.77 MJ·m-3. Notably, the integration of polyphenol lignin synergistically improved the thermal stability, water resistance, UV-blocking performances of ELCF. Importantly, after immersion for 30 d, ELCF still possessed high wet strength of 70.38 MPa, and elongation at break of 7.70 %, suggesting excellent and durable mechanical performances. Moreover, ELCF could be biodegraded in the natural soil. Therefore, this study provides a new and versatile approach to reconstruct highly-performance lignocellulosic films coupling strength, toughness with flexibility for promising plastic replacement.

Stereocontrolled Synthesis of 2-Deoxy- C-glycopyranosyl Arenes Using Glycals and Aromatic Amines.

An efficient and stereoselective one-pot, two-step tandem α-arylation of glycals from readily available aryl amines via stable diazonium salts has been developed. Moreover, the stereoselective preparation of the challenging ß- C-glycosyl arenes by the anomerization of α- C-glycosides using HBF4 is also described. This protocol has a broad substrate scope and a wide functional-group tolerance. It can be used for the gram-scale preparation of 3-oxo- C-glycosides, which are versatile substrates for the preparation of many biologically important C-glycosides.