Enantioselective Crystallization of Diglycerol Dicarbonate: Impact of the Microstructure on Polyhydroxyurethane Properties.

Bicylic carbonates are precursors employed in non-isocyanate polyurethane syntheses, namely polyhydroxyurethanes (PHUs) and, among them, ether-activated biobased diglycerol dicarbonate (DGDC) is widely investigated. Herein, the original separation of DGDC stereoisomers, thanks to a recrystallization procedure, leading to enantiomers having different crystal lattices, that is, square transparent crystals and needle-like structures, respectively, is reported. In this study, the separation and the characterization of the two crystal structures is first discussed and, second, the impact of the stereochemistry of DGDC on the corresponding PHUs properties is investigated.

Versatile cross-linked fatty acid-based polycarbonate networks obtained by thiol-ene coupling reaction.

Bio-sourced polycarbonate networks have been synthesized from an alkene-functional fatty-acid based polycarbonate precursor. Cross-linked networks were created using the radical thiol-ene coupling reaction. The resulting polycarbonate materials exhibited versatile properties either influenced by the structure of the cross-linker or the cross-linker/olefin unit ratio.

Synthesis and Self-Assembly of Xylan-Based Amphiphiles: From Bio-Based Vesicles to Antifungal Properties.

This work aims at designing functional biomaterials through selective chemical modification of xylan from beechwood. Acidic hydrolysis of xylan led to well-defined oligomers with an average of six xylose units per chain and with an aldehyde group at the reductive end. Reductive amination was performed on this aldehyde end group to introduce an azide reactive group.

Simple and Efficient Approach toward Photosensitive Biobased Aliphatic Polycarbonate Materials.

Fatty acids were used as precursors for the synthesis of photosensitive polycarbonate materials. In order to avoid multistep reactions, a simple and straightforward methodology toward the synthesis of photosensitive monomers has been developed. Hence, a fatty acid-based cyclic carbonate bearing an unsaturation was synthesized and subsequently polymerized in a controlled manner ( = 1.

Bleaching Earths as Powerful Additives for Ru-Catalyzed Self-Metathesis of Non-Refined Methyl Oleate at Pilot Scale.

A practical and cost-effective ruthenium-catalyzed self-metathesis of non-refined methyl oleate (85 %) derived from very high oleic sunflower oils was demonstrated at pilot scale using a robust and kg-scale commercially available SIPr-M71 pre-catalyst. The simple addition of 1 wt % bleaching earths (Tonsil 110FF) to a thermally pretreated oil could efficiently prevent catalyst deactivation. Remarkably, without the need for filtration, the catalytic system was able to achieve a turnover number (TON) of more than 744 000 at a catalyst loading of only 1 ppm.

Periodate oxidation of 4-O-methylglucuronoxylans: Influence of the reaction conditions.

This work aims at studying the sodium periodate oxidation of 4-O-methylglucuronoxylans (MGX) in different experimental conditions for a control of the oxidation degree. A series of sodium periodate oxidation reactions were conducted at three NaIO4/xylose molar ratios: 0.05, 0.

Total synthesis and biological evaluation of the cytotoxic resin glycosides ipomoeassin A-F and analogues.

A multitasking C-silylation strategy using the readily available compound 26 as a surrogate for cinnamic acid represents the key design element of a total synthesis of all known members of the ipomoeassin family of resin glyosides. This protecting group maneuver allows the unsaturated acids decorating the glucose subunit of the targets to be attached at an early phase of the synthesis, prevents their participation in the ruthenium-catalyzed ring-closing metathesis (RCM) used to form the macrocyclic ring, and protects them against reduction during the hydrogenation of the resulting cycloalkene over Wilkinson's catalyst. As the C-silyl group can be concomitantly removed with the O-TBS substituent using tris(dimethylamino)sulfonium difluorotrimethylsilicate (TASF) in acetonitrile, no separate protecting group manipulations were necessary in the final stages, thus contributing to a favorable overall "economy of steps".

Reusable catalysts for the asymmetric Diels-Alder reaction.

A new method for recycling chiral bis(oxazoline)-copper complexes is described based on the formation of charge-transfer complexes, their subsequent precipitation, and reuse after addition of new substrates. The conditions to perform this procedure were optimized in the presence of three bis(oxazoline)-based ligands. When associated with copper salts, these ligands efficiently catalyzed the Diels-Alder reaction between cyclopentadiene and alpha,beta-unsaturated acyloxazolidinones.

A new method for recycling asymmetric catalysts via formation of charge transfer complexes.

[reaction: see text]. A new concept for recycling asymmetric bis(oxazoline)-type catalysts is reported. The formation of charge-transfer complexes between the chiral ligand and trinitrofluorenone and their subsequent precipitation and reuse by addition of new substrate solutions is described.