ChemInform Abstract: REACTION OF SUGAR DERIVATIVES WITH α‐DIHALO ETHERS. SYNTHESIS OF GLYCOSYL CHLORIDES WITH THE REAGENT DICHLOROMETHYL METHYL ETHER‐TIN TETRACHLORIDE
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Abstract Bei Reaktion der Per‐O‐acetate von β‐D‐Xylopyranose, α‐ und β‐D‐Glucopyranose, β‐D‐Galactopyranose, β‐D‐Mannopyranose, L‐Rhamnose, β‐Lactose, β‐Maltose, α‐Cellobiose, β‐Gentiobiose und β‐Rutinose mit dem im Titel erwähnten Reagenz entstehen die entsprechenden α‐Aceto chlorzucker in 65‐97proz. Ausbeute.Keywords:
Tetrachloride
Titanium tetrachloride
The addition of allyltriphenylstannane to 3-sulfinylfurfural (3) in the presence of titanium(1V) tetrachloride proceeded with high diastereoselectivity to give the furyl alcohol (6).whereas the similar treatment with tin(lV) tetrachloride afforded the other diastereoisomeric alcohol (7), exclusively.Lewis acid-promoted allylation of aldehydes using allylmetal compounds such as allyltrialkylsilanes and allyltriarylstannanes has been widely studied.'From the view point of asymmetric reactions, there have been a number of reports which inchode thr use of allylmetal compounds bearing chiral l i g a n d ~, ~ chiral aldehydes3and chiral Lewis acid mediator^.^In the course of our studies on the asymmetric cycloaddition employing chiral sulfoxides,5 we were intrigued by the use of a chiral sulfinyl furfural for the reaction mediated by a Lewis acid.Despite of numerous efforts6 for asymmetric condensations using a-sulfinyl carbonyl compounds, little work has been done on the asymmetric addition to P-sulfinyl carbonyl compounds.This is presumably because of its low performance in chelation control.3aOur interest in Lewis acid-mediated reactions prompted us to investigate the possibility of asymmetric condensation of P-sulfinyl carbonyl compounds.Reported herein is a highly diastereoselective condensation of P-sulfinyl carbonyl compounds (i.e.3-sulfinyl furfural) with aliyltriphenylstannane in the presence of a Lewis acid.
Titanium tetrachloride
Tetrachloride
Sulfonium
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Disaccharide
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Reductive amination
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The thermophilic and cellulolytic fungus Humicola sp. secretes amylase in the liquid culture medium. This activity is induced by starch, maltose and cellobiose. Glucose impairs accumulation of amylolytic activity in the culture medium. The enzyme hydrolyzes starch, maltose and pullulan to glucose as the end-product.
Pullulan
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Of the yeasts that ferment D-glucose anaerobically, over 40% can use certain glycosides and D-galactose oxidatively, but cannot ferment them. This phenomenon is here called the Kluyver effect. More than half the yeast species described which exhibit this effect do so with more than one substrate. Yeasts showing the effect with maltose, cellobiose and D-galactose were compared with fermenting strains, to determine whether enzyme inactivation or cessation of sugar uptake was responsible. The different responses of the yeasts to anaerobic conditions, with respect to their enzymic activity, sugar uptake and CO2 production, consistently showed that the Kluyver effect resulted from the requirement of transport for oxygen, and this seems to be the common explanation throughout the yeasts.
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Enzymatic Hydrolysis
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Cellobiose and maltose were nitrated and their properties studied to note the effect of the difference in glycosidic linkage (β- and α-respectively). Cellobiose octanitrate is more stable than maltose octanitrate as measured by the Abel test, and both are less stable than cellulose and starch nitrates. Neither of the octanitrates is sufficiently stable to permit of the application of the Bergmann–Junk test. If the stability of the cellulose nitrate building unit, namely, cellobiose octanitrate, carries over into its polymeric form, it would be expected that cellulose nitrate (characterized by 1,4-β-glucosidic linkages) should be inherently more stable than starch nitrate (α-1,4-glucosidic linkages).
Glycosidic bond
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Oligosaccharide
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Co-ordination complexes between diesters of α,ω-dicarboxylic acids and titanium tetrachloride, tin tetrachloride, and zirconium tetrachloride have been prepared. The analytical results, the infrared spectra, the melting points, and the molecular-weight determinations indicate that for the titanium and zirconium complexes, two types of complexes are obtained, one having a general formula MX 4• 1 diester in which chelate rings from five to nine atoms are formed and the other one, 2MX 4• 1 diester in which there are two 4-membered rings per complex molecule. With tin tetrachloride only one type of complex is formed, which has two tin tetrachlorides and two diesters per complex molecule.
Tetrachloride
Titanium tetrachloride
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