Renewable benzoxazine monomer from Vanillin: Synthesis,characterization, and studies on curing behavior

A novel renewable based benzoxazine, 3‐(furan‐2‐ylmethyl)?8‐methoxy‐3,4‐dihydro‐2H‐1,3‐benzoxazine‐6‐formyl (Va‐Bz), has been synthesized from a lignin derived chemical “vanillin” without solvents. Poly (Va‐Bz) has high Tg and excellent thermal and adhesive properties. A mechanism of cross‐linking, due to electrophilic substitution at furan and decarboxylation of carboxylic group of benzene ring, is suggested. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 7–11     

Modular Stereoselective Synthesis of (1→2)‐C‐Glycosides based on the sp2–sp3 Suzuki–Miyaura Reaction

This work reports a modular and rapid approach to the stereoselective synthesis of a variety of α‐ and β‐(1→2)‐linked C‐disaccharides. The key step is a Ni‐catalyzed cross‐coupling reaction of D ‐glucal pinacol boronate with alkyl halide glycoside easily prepared from commercially available D ‐glucal. The products of this sp²–sp³ cross‐coupling reaction can be converted to glucopyranosyl, mannopyranosyl, or 2‐deoxy‐glucopyranosyl C‐mannopyranosides by one‐ or two‐step stereoselective oxidative–reductive transformations. To the best of our knowledge, we demonstrated the first synthetic application of a challenging sp²–sp³ Suzuki‐Miyaura cross‐coupling reaction in carbohydrate chemistry.     

Chiral ethylene-bridged flavinium salts: the stereoselectivity of flavin-10a-hydroperoxide formation and the effect of substitution on the photochemical properties

A series of chiral non-racemic N¹,N¹⁰-ethylene bridged flavinium salts 4 was prepared using enantiomerically pure 2-substituted 2-aminoethanols (R?=?isopropyl, phenyl, benzyl, 4-methoxybenzyl, 4-benzyloxybenzyl) derived from amino acids as the sole source of chirality. The flavinium salts were shown to form 10a-hydroperoxy- and 10a-methoxy-adducts with moderate to high diastereoselectivity depending on the ethylene bridge substituent originating from the starting amino acid. High diastereoselectivities (dr values from 80:20 to >95:5) were observed for flavinium salts bearing benzyl substituents attached to the ethylene bridge. The benzyl group preferred the face-to-face (syn) orientation relative to the flavinium unit; thereby effectively preventing nucleophilic attack from one side. This conformation was found to be the most stable according to the DFT calculations. Consequently, the presence of benzyl groups causes intermolecular fluorescence quenching resulting in a significant decrease in the fluorescence quantum yield from 11% for 4a bearing an isopropyl substituent to 0.3% for 4c containing a benzyl group and to a value lower than 0.1% for the benzyloxybenzyl derivative 4e.     

Enhancing Tumor Cell Response to Chemotherapy through the Targeted Delivery of Platinum Drugs Mediated by Highly Stable,Multifunctional Carboxymethylcellulose‐Coated Magnetic Nanoparticles

The fabrication of nanoparticles using different formulations, and which can be used for the delivery of chemotherapeutics, has recently attracted considerable attention. We describe herein an innovative approach that may ultimately allow for the selective delivery of anticancer drugs to tumor cells by using an external magnet. A conventional antitumor drug, cisplatin, has been incorporated into new carboxymethylcellulose‐stabilized magnetite nanoparticles conjugated with the fluorescent marker Alexa Fluor 488 or folic acid as targeting agent. The magnetic nanocarriers possess exceptionally high biocompatibility and colloidal stability. These cisplatin‐loaded nanoparticles overcome the resistance mechanisms typical of free cisplatin. Moreover, experiments aimed at the localization of the nanoparticles driven by an external magnet in a medium that mimics physiological conditions confirmed that this localization can inhibit tumor cell growth site‐specifically.     

Resistance of nanostructured films to permeation by industrial pollutants

The aim of this study was to modify or replace the PEVA foil (polyethylenevinylacetate) currently used in the Czech Army as a construction material for the NBC protective disposable suit JP-90 (a part of the OM-90 protective mask set). This material shows inadequate protective properties; therefore, barrier coatings based on melamine, Parylene (polyparaxylylene) and various types of SiO _x were applied to its surface by vacuum technologies. The selected samples coated with polymer matrix barrier nanocoatings were continuously evaluated for resistance to permeation by highly toxic chemicals warfare agents (CWAs) and industrial pollutants at the Military Technical Institute of Protection (MTIP) in Brno. In addition, the microstructure of selected samples was assessed before and after the exposure to pollutants. The nanocoatings thus prepared were characterised in terms of surface morphology (SEM), chemical structure (FTIR), and oxygen transmission rate (OTR) at the Faculty of Chemistry, Brno University of Technology. Sulphur mustard (HD) was used to test the sample resistance to permeation. Cyclohexane and subsequently 1,6-dichlorhexane were used as substitute testing substances for HD; however, the latter proved to be more advantageous. The resulting OTR values are presented, along with the permeation by toxic substances, both for the initial uncoated and the barrier-layers-coated PEVA foil. The results show a difference in the mechanism of vapour permeation of CWAs and toxic volatile organic solvents (VOCs).