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Fermentative bioethanol production from pyrolytic sugars was improved via aromatics removal by liquid-liquid extraction. As solvents, the ionic liquid (IL) trihexyltetradecylphosphonium dicyanamide (P666,14[N(CN)2]) and ethyl acetate (EA) were compared. Two pyrolytic sugar solutions were created from acid-leached and untreated pinewood, with levoglucosan contents (most abundant sugar) of 29.0% and 8.3% (w/w), respectively. In a single stage extraction, 70% of the aromatics were effectively removed by P666,14[N(CN)2] and 50% by EA, while no levoglucosan was extracted. The IL was regenerated by vacuum evaporation (100mbar) at 220°C, followed by extraction of aromatics from fresh pyrolytic sugar solutions. Regenerated IL extracted aromatics with similar extraction efficiency as the fresh IL, and the purified sugar fraction from pretreated pinewood was hydrolyzed to glucose and fermented to ethanol, yielding 0.46g ethanol/(g glucose), close to the theoretical maximum yield., (Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Carbohydrate sources play important roles in energy and growth of plants. Therefore, in this study, we investigated the optimal carbohydrate source in hairy root cultures (HRCs) of Scutellaria baicalensis infected with Agrobacterium rhizogenes strain R1000. The hairy roots were cultured in half-strength B5 liquid medium supplemented with seven different carbohydrates sources (sucrose, fructose, glucose, galactose, sorbitol, mannitol and maltose), each at a concentration of 100 mM, in order to identify the best carbon sources for the production of major flavones, such as wogonin, baicalin and baicalein. Sucrose, galactose and fructose markedly influenced the production of major flavones and were therefore chosen for subsequent experiments. HRC growth and flavone accumulation were examined following culture with 30, 100 and 150 mM sucrose, galactose and fructose, respectively. From these data, 150 mM sucrose was found to be the optimal carbon source for the enhancement of baicalein production and growth of S. baicalensis HRCs. Fructose caused the greatest increase in baicalin accumulation. Additionally, galactose was the optimal carbon source for wogonin production. These results provide important insights into the optimal growth conditions, particularly the appropriate carbohydrate source, for S. baicalensis.

Cyclopropylmethylidene has been developed as a versatile protecting group for carbohydrate synthesis. It can be formed by acid-catalyzed acetalization between cyclopropanecarboxaldehyde and 1,3-diols of sugar molecules. Selective reductive opening of the 4,6-O-cyclopropylmethylidene can be achieved to afford a C4 free hydroxyl group and a C6-cyclopropylmethyl (CPM) ether or vice versa. The cyclopropylmethylidene was found to be less stable than benzylidene under acidic conditions. [ABSTRACT FROM AUTHOR]

A total synthesis of the trisaccharide repeat unit of Salmonella serogroup E1 O‐antigen is reported. This synthesis features a key β‐mannosylation reaction through a cesium carbonate‐mediated anomeric O‐alkylation of a partially protected D‐mannose with an L‐fucose‐derived electrophile for the first time. [ABSTRACT FROM AUTHOR]

Several structurally diverse d‐mannose‐derived lactols, including various deoxy‐d‐mannoses and conformationally restricted bicyclic d‐mannoses, have been synthesized and investigated in mechanistic studies of β‐mannosylation through Cs2CO3‐mediated anomeric O‐alkylation. It was found that deoxy mannoses or conformationally restricted bicyclic d‐mannoses are not as reactive as their corresponding parent mannose. This type of β‐mannosylation proceeds efficiently when the C2‐OH is left free, and protection of that leads to inferior results. NMR studies of d‐mannose‐derived anomeric cesium alkoxides indicated the predominance of the equatorial β‐anomer after deprotonation. Reaction progress kinetic analysis suggested that monomeric cesium alkoxides be the key reactive species for alkylation with electrophiles. DFT calculations supported that oxygen atoms at C2, C3, and C6 of mannose promote the deprotonation of the anomeric hydroxyl group by Cs2CO3 and chelating interactions between Cs and these oxygen atoms favor the formation of equatorial anomeric alkoxides, leading to the highly β‐selective anomeric O‐alkylation. Based on experimental data and computational results, a revised mechanism for this β‐mannosylation is proposed. The utilization of this β‐mannosylation was demonstrated by an efficient synthesis of the hexasaccharide core of complex fucosylated N‐linked glycans. [ABSTRACT FROM AUTHOR]

Development of efficient, mild, and easily operable stereoselective glycosylations is of critical importance to access sufficient amounts of pure and structurally well-defined carbohydrates for studies of their biological functions. Such studies will facilitate our understanding of the role of complex oligosaccharides and glycoconjugates in biological processes as well as the development of carbohydrate-based effective therapeutic agents. This review highlights recent advances in the transition metal catalyzed stereoselective glycosylations for the synthesis of a variety of structurally complex and biologically significant O-, N-, C-, and S-glycosides. [ABSTRACT FROM AUTHOR]

This review summarizes recent accomplishments involving transition metal catalysis in efficient and stereoselective O-glycosylation reactions. In addition, proposed mechanisms of each catalytic O-glycosylation are discussed respectively. [ABSTRACT FROM AUTHOR]

2-Deoxy sugars exist in numerous bioactive molecules and exert significant influences on their physical, chemical, and biological properties. Due to the absence of directing group at C-2 and the labile nature of glycosidic linkages, stereoselective construction of 2-deoxy glycosides is rather challenging. Despite the fact that remarkable success in the synthesis of 2-deoxy sugars were achieved using indirect routes, direct synthesis of 2-deoxy glycosides has been extensively explored in order to improve overall synthetic efficiency through eliminating extra pre- and post-glycosylation steps. In this account, we have summarized advances in direct synthesis of 2-deoxy glycosides reported in the last decade, with an emphasis on those efforts published in last five years. In addition, some recent reports in stereoselective synthesis of 2-deoxy thioglycosides have also been discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

Substituted benzyl ethers have been widely used as readily manipulatable protecting groups for organic synthesis. It is known that electron-rich para -methoxybenzyl (PMB) ethers can be selectively deprotected over benzyl or other electron-poor benzyl ethers under oxidative conditions. In this presentation, we will describe an approach for selective deprotection of benzyl ethers in the presence of PMB ethers under reductive conditions. This new method should complement the existing strategies in the utilization of substituted benzyl ethers in organic synthesis, especially in carbohydrate synthesis. [ABSTRACT FROM AUTHOR]

Review: [196 refs. [ABSTRACT FROM AUTHOR]

An efficient method for chemoselective deprotection of benzyl ethers in the presence of 4-methoxybenzyl ethers using radical anion reductant lithium 4,40-di-tert-butylbiphenyl is developed. [ABSTRACT FROM AUTHOR]

Review: 122 refs. [ABSTRACT FROM AUTHOR]

[Display omitted] Stereoselective construction of a variety of β-glycosides can be achieved using abundant and inexpensive K 2 CO 3 -mediated stereoselective anomeric O-alkylation of sugar lactols with primary electrophiles. In addition, application of this methodology to the synthesis of various azido-modified glycosphingolipids has been accomplished in good yields and excellent anomeric selectivity using sphingosine-derived primary triflate. [ABSTRACT FROM AUTHOR]