- Synthesis of blockwise alkylated (1→4) linked trisaccharides as surfactants: Influence of configuration of anomeric position on their surface activities
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New carbohydrate-based surfactants consisting of hydrophilic cellobiosyl and hydrophobic glucosyl residues, methyl β-D-glucopyranosyl-(1→4)- α-D-glucopyranosyl-(1→4)-2,3,6-tri-O-methyl-α-D- glucopyranoside 1 (GβGαMα, G: glucopyranosyl residue, α and β: α-(1→4)- and β-(1→4) glycosidic bonds, M: methyl group), 2 (GβGβMα), 3 (GβGαMβ), 4 (G βGβMβ), 5 (G βGαEα, E: ethyl group), 6 (GβGβEα), 7 (G βGαEβ), 8 (G βGβEβ) and eight α-and β-glycoside mixtures (a mixture of 1 and 2: 1/2 = 62/38 (9), 32/68 (10); a mixture of 3 and 4: 3/4 = 69/31 (11), 32/68 (12); a mixture of 5 and 6: 5/6 = 62/38 (13), 33/67 (14); a mixture of 7 and 8: 7/8 = 59/41 (15), 29/71 (16)) were synthesized via combined methods consisting of acid-catalyzed alcoholysis of cellulose ethers and glycosylation of phenyl thio-cellobioside derivatives. Their surface activities in aqueous solution depended on their chemical structures: α- or β-(1→4) linkage between hydrophilic cellobiosyl and hydrophobic glucosyl blocks, methyl or ethyl groups of hydrophobic glucosyl block, and α- or β-linked ether group at the C-1 of hydrophobic glucosyl block. The mixing effect of α- and β-glycosides on surface activities was also investigated. As a result, ethyl β-D-glucopyranosyl-(1→4)-α-Dglucopyranosyl-(1→4)-2,3, 6-tri-O-ethyl-β-D-glucopyranoside 7 (GβG αEβ) had the highest surface activity, and its critical micellar concentration (CMC) and γCMC (surface tension at CMC) values of compound 7 were 0.5 mM(ca. 0.03 wt %) and 34.5 mN/m, respectively. The surface tensions of α- and β-glycoside mixtures except for compounds 9 and 10 were almost equal to those of pure compounds. The syntheses of the mixtures of α- and β-glycosides without purification process are easier than those of pure compounds. Thus, the mixtures should be more practical compounds for industrial use as a surfactant.
- Nakagawa, Atsushi,Kamitakahara, Hiroshi
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p. 1671 - 1683
(2011/11/12)
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- Defining oxyanion reactivities in base-promoted glycosylations
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Saccharide oxyanions obtained by base treatment could be employed in glycosylation to give oligosaccharides with high stereo- and regioselectivities.
- Matwiejuk, Martin,Thiem, Joachim
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p. 8379 - 8381
(2011/09/14)
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- Hydrogenolysis of the 4,6-o-ketals of glucopyranosides. Configuration-dependent high regio- and stereo-selectivity of the diastereoisomeric acetophenone derivatives
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Hydrogenolysis (reductive cleavage) of the (R) isomers of the acetophenone 4,6-O-derivatives of glucopyranosides with LiAlH4/AlCl3 gives the 4-O-(1′-phenylethyl) ethers with (R) configuration; the corresponding (5) isomers produce the respective (R) 6-O-(1′-phenylethyl) ethers are produced. The hydrogenolysis of other 4,6-O-ketals affords O 4 ether derivatives; the two diastereoisomeric 4,6-O-s-butylidene derivatives (cyclic ketals) give O 4-ethers with the opposite absolute configuration. The stereoselectivity of these reactions is explained by the development of a four-centre transition state. The absolute configuration of the ethers has been determined by means of circular dichroism measurements.
- Hajko, Janos,Szabovik, Gabriella,Kerekgyarto, Janos,Kajtar, Marton,Liptak, Andras
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p. 357 - 363
(2007/10/03)
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