Saccharides dehydration

Carlini, C., Giuttari, M., Galletti, A. M. R., Sbrana, G., Armaroli, T., and Busca, G., Selective saccharides dehydration to 5-hydroxymethyl-2-furaldehyde by heterogeneous niobium catalysts. Appl Catalysis A-Geneml 1999, 183 (2), 295-302. 

Yang F, Liu Q, Yue M, Bai X, Du Y (2011) Tantalum compounds as heterogeneous catalysts for saccharide dehydration to 5-hydroxymethylfurfural. Chem Conunun 47 4469-4471... 

Mild benzhydrylation (diphenylmethylation) of primary and secondary saccharide alcohols, and tritylation of the primary alcohols, were promoted by 4A AW-300 MS at room temperature through a dehydration mechanism in the absence of any strong protic or Lewis acid. While protection of a single primary or secondary hydroxyl... 

Heterogeneous catalysts, particularly zeolites, have been found suitable for performing transformations of biomass carbohydrates for the production of fine and specialty chemicals.123 From these catalytic routes, the hydrolysis of abundant biomass saccharides, such as cellulose or sucrose, is of particular interest. The latter disaccharide constitutes one of the main renewable raw materials employed for the production of biobased products, notably food additives and pharmaceuticals.124 Hydrolysis of sucrose leads to a 1 1 mixture of glucose and fructose, termed invert sugar and, depending on the reaction conditions, the subsequent formation of 5-hydroxymethylfurfural (HMF) as a by-product resulting from dehydration of fructose. HMF is a versatile intermediate used in industry, and can be derivatized to yield a number of polymerizable furanoid monomers. In particular, HMF has been used in the manufacture of special phenolic resins.125... 

Chheda, J.N., Roman-Leshkov, Y. and Dumesic, J.A. 2007. Production of 5-Hydroxymethylfurfural and Furfural by Dehydration of Biomass-Derived Mono- and Poly-Saccharides. Green Chem., 9, 342-350. 

Saline laxatives (magnesium citrate, magnesium sulfate, sodium sulfate, and disodium phosphate) or saccharide laxatives (sorbitol, mannitol, lactulose) are also used in poisoned patients. Common adverse effects are abdominal cramps, excessive diarrhea, and abdominal distension. Dehydration and electroljde imbalance in children, and hjrpermagnesemia and magnesium toxicity (with magnesium-based cathartics) have also been reported. 

Anhydrosugars can be utilized for the synthesis of some derivatives, such as amino sugars and others. Dehydration is the first step of sugar caramelization. Further heating of dehydrated saccharides results in the formation of three subsequent compounds called caramelan, caramelen, and caramelin (Tomasik et al., 1989) ... 

In strongly acidic media, saccharides produce furan derivatives in a sequence of reactions that are rearrangements and dehydrations followed by cyclization. Similar products are available thermally. Pentoses and hexoses give furan-2-aldehyde and 5-hydroxymethylfuran-2-aldehyde, respectively. Both of these products are responsible for the specific aroma of caramel and burnt sugar. 

Formation of Pyrazoles from Bis(hydrazones).—Mesoxaldehyde bis(phenylhydrazone) (193), obtained by periodate oxidation of saccharide osazones (192) is readily cyclized in the presence of acids to give l-phenyl-4-phenylazo-pyrazole (195).162 365 Hexulose phenylosazones (192) are also disproportionaled in the presence of acidic salts of carbonyl reagents, such as hydroxylamine hydrochloride, to give l-phenyl-4-phenylazo-pyrazolin-5-one (196). The reaction probably proceeds via mesoxalic acid 1,2-bis(phenylhydrazone) (194).365 The hydroxalkyl derivatives of 196 are produced from dehydroascorbic acid bis(phenylhydrazone) by treatment with base to open the lactone ring and permit the conversion of 197 to 199.351,366 Another type of pyrazole that is formed by dehydrating osazones with acetic anhydride is discussed later under anhydroosazones (see Schemes 45,53). 

Di- and oligo-saccharide derivatives are less sensitive to dehydration reactions in the course of the Maillard reaction, and contribute less to color formation, as compared to the respective monosaccharides. ... 

Chheda IN, Roman-Leshkov Y, Dumesic JA (2007) Production of 5-hydroxymethylfurfural and furfural by dehydration of biomass-derived mono- and poly-saccharides. Green Chem... 

Stronger. The increased B-N interaction causes the N-H proton to become more acidic. Therefore at pH 11.32, the saccharide-boronate complex dehydrates (loss of from aniline and OH from boronate) to produce a red species with a covalent B-N bond. 

Formation of functionalized carbonaceous materials, such as saccharides, starch, sucrose, and glucose, has been observed by hydrothermal carbonization of cellulose at 220-250°C [115]. The formation of this material follows essentially the path of a hydrolysis followed by dehydration and fragmentation into soluble (monomer) products [115]. Shu-Hong Yu and Titirici extensively studied the hydrothermal carbonization of biomass and the mechanisms of char formation. The chemical reactions of biomass (e.g., saccharides, cellulose, lignins) involved in the hydrothermal process are complex in nature and most of the reports focus on initial steps of the reaction, such as hydrolysis, dehydration, and decarboxylation. Recently, formation of polymerization and aromatization in cellulose hydrothermal carbonization has been described, too [36,178,179]. 

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