The (TMEDA)I·I3 complex as a new radical initiator for the perfluoroalkylation of RSH.

The development of biorefinery processes to platform chemicals for most lignocellulosic substrates, results in side processes to intermediates such as oligosaccharides. Agrofood wastes are most amenable to produce such intermediates, in particular, cellooligo-saccharides (COS), pectooligosaccharides (POS), xylooligosaccharides (XOS) and other less abundant oligomers containing mannose, arabinose, galactose and several sugar acids. These compounds show a remarkable bioactivity as prebiotics, elicitors in plants, food complements, healthy coadyuvants in certain therapies and more. They are medium to high added-value compounds with an increasing impact in the pharmaceutical, nutraceutical, cosmetic and food industries. This review is focused on the main production processes: autohydrolysis, acid and basic catalysis and enzymatic saccharification. Autohydrolysis of food residues at 160-190 • C leads to oligomer yields in the 0.06-0.3 g/g dry solid range, while acid hydrolysis of pectin (80-120 • C) or cellulose (45-180 • C) yields up to 0.7 g/g dry polymer. Enzymatic hydrolysis at 40-50 • C of pure polysaccharides results in 0.06-0.35 g/g dry solid (DS), with values in the range 0.08-0.2 g/g DS for original food residues.Fermentation 2020, 6, 31 2 of 27 forestall engineering approaches, to name a few. Lignocellulosic biomass, of any origin is, therefore, a most promising raw material for biorefineries, considering such facilities as integrated refineries turning biomass into fuels, platform chemicals, food, feed and materials using integrated processes with an optimized used of resources [4]. This vision can be extended to resources of aquatic origin (seaweed, seagrass and microalgae) as well as residues from livestock [5,6]. In general, apart from forestall and energy crops biomass, most of it depends on the production of biomass and, in particular, food wastes [7,8]. While more than 100,000 M tons of biomass wastes are yearly produced [7], wastes strictly considered as food wastes (foods not consumed from any part of the food supply chain or any part of the food that is non edible and, therefore, becomes a residue) account for more than 1300 M tons each year [8]. The valorization of biomass wastes into a plethora of useful energy vectors, chemical compounds and ingredients receives a notable amount of interest from all stakeholders, including researchers and entrepreneurs. They are a source to several value-added products, such as monosaccharides (glucose, xylose, mannose, fructose, arabinose and more), oligosaccharides (fructoor FOS, xylo-or XOS, galacto-or GOS, galacturonic-or GALOS, lactosucrose, etc.), biofuels (ethanol, butanol, dimethylether -DME-, biodiesel, hydrogen), bioactive compounds (flavonoids, phenolic acids, terpenes, terpenoids, carotenoids), nanocellulose (bacterial, wood-related), lignin and its derivatives (a source of aromatics from biomass and prospective substitute of the aromatic or BTEX fraction produced in oil refineries) [8]. Oligomers from cellulose, hemicellulose, lignin, pectin and oth...

The synthesis of mono and divalent β-galactosylamides linked to a hydroxylated chain having a C2 symmetry axis derived from l-tartaric anhydride is reported. Reference compounds devoid of hydroxyl groups in the linker were also prepared from β-galactosylamine and succinic anhydride. After functionalization with an alkynyl residue, the resulting building blocks were grafted onto different azide-equipped scaffolds through the copper catalyzed azide-alkyne cycloaddition. Thus, a family of structurally related mono and divalent β-N-galactopyranosylamides was obtained and fully characterized. The binding affinities of the ligands towards the model lectin PNA were measured by the enzyme-linked lectin assay (ELLA). The IC values were significantly higher than that of galactose but the presence of hydroxyl groups in the aglycone chain improved lectin recognition. Docking and molecular dynamics experiments were in accordance with the hypothesis that a hydroxyl group properly disposed in the linker could mimic the Glc O3 in the recognition process. On the other hand, divalent presentation of the ligands led to lectin affinity enhancements.

SummaryIn this work we describe the synthesis of mono- and divalent β-N- and β-S-galactopyranosides and related lactosides built on sugar scaffolds and their evaluation as substrates and inhibitors of the Trypanosoma cruzi trans-sialidase (TcTS). This enzyme catalyzes the transfer of sialic acid from an oligosaccharidic donor in the host, to parasite βGalp terminal units and it has been demonstrated that it plays an important role in the infection. Herein, the enzyme was also tested as a tool for the chemoenzymatic synthesis of sialic acid containing glycoclusters. The transfer reaction of sialic acid was performed using a recombinant TcTS and 3’-sialyllactose as sialic acid donor, in the presence of the acceptor having βGalp non reducing ends. The products were analyzed by high performance anion exchange chromatography with pulse amperometric detection (HPAEC-PAD). The ability of the different S-linked and N-linked glycosides to inhibit the sialic acid transfer reaction from 3’-sialyllactose to the natural substrate N-acetyllactosamine, was also studied. Most of the substrates behaved as good acceptors and moderate competitive inhibitors. A di-N-lactoside showed to be the strongest competitive inhibitor among the compounds tested (70% inhibition at equimolar concentration). The usefulness of the enzymatic trans-sialylation for the preparation of sialylated ligands was assessed by performing a preparative sialylation of a divalent substrate, which afforded the monosialylated compound as main product, together with the disialylated glycocluster.

The supramolecular self-assembly mode of two diacyl-glycoamphiphiles depends on the length of the flexible achiral ethoxylated linker.

The synthesis of multivalent sialylated glycoclusters is herein addressed by a chemoenzymatic approach using the trans-sialidase of Trypanosoma cruzi (TcTS). Multivalent β-thio-galactopyranosides and β-thio-lactosides were used as acceptor substrates and 3'-sialyllactose as the sialic acid donor. High performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was shown to be an excellent technique for the analysis of the reaction products. Different eluting conditions were optimized to allow the simultaneous resolution of the sialylated species, as well as their neutral precursors. The TcTS efficiently transferred sialyl residues to di, tri, tetra and octa β-thiogalactosides. In the case of an octavalent thiolactoside, up to six polysialylated compounds could be resolved. Preparative sialylation reactions were performed using the tetravalent and octavalent acceptor substrates. The main sialylated derivatives could be unequivocally assigned by MALDI mass spectrometry. Inhibition of the transfer to the natural substrate, N-acetyllactosamine, was also studied. The octalactoside caused 82 % inhibition of sialic acid transfer when we used equimolar concentrations of donor, acceptor and inhibitor.

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Carbohydrate-protein interactions are involved in a myriad of biological processes. Thus, glycomimetics have arisen as one of the most promising synthetic targets to that end. Within the broad variety of glycomimetics, thiodisaccharides have proven to be excellent tools to study these processes, and even more, some of them unveiled interesting biological activities. This review brings together research made on the introduction of N-acetylhexosamine residues into thiodisaccharides to date, passing through classic substitution (as S N 2, thioglycosylation and ring-opening reactions) and addition (as thiol-ene coupling and Michael-type additions) reactions. Recent and interesting developments regarding addition reactions to vinyl azides, cross-coupling reactions and novel chemoenzymatic methods are also discussed.