Topic
Glucal
About: Glucal is a research topic. Over the lifetime, 590 publications have been published within this topic receiving 8960 citations. The topic is also known as: D-glucal.
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TL;DR: In this paper, the regioselectivity of the triol 4 by the diazirine 1 is predicted on the basis of two assumptions: preferred protonation of the intermediate glycosylidene carbene by the OH group involved in the weakest intramolecular H-bond, and attack in the π-plane of the thereby generated oxycarbenium cation either by the reoriented oxy anion, or by a properly oriented vicinal OH group.
Abstract: Hydrogen bonding of the triol 4 in chlorinated solvents was studied by IR (CH2Cl2 and CCl4) and 1H-NMR spectroscopy (CDCl3), and the regioselectivity of the glycosidation of the triol 4 by the diazirine 1 is predicted on the basis of two assumptions: preferred protonation of the intermediate glycosylidene carbene by the OH group involved in the weakest intramolecular H-bond, and attack in the π-plane of the thereby generated oxycarbenium cation either by the reoriented oxy anion, or by a properly oriented vicinal OH group. Glycosidation led to the disaccharides 5–10 (Scheme) which were separated and characterized as their acetates 11–16, to the lactone azines 17 and to the 2-(benzyloxy)glucal 18. In agreement with the predictions, glycosidation in non-coordinating solvents gave the 1,2-, 1,3-, and 1,4-linked disaccharides in decreasing relative amounts. Glycosidation in THF proceeded with a lower degree of regioselectivity and led preferentially to the β -D-anomers, except for the minor, 1,4-linked disaccharides, where THF had only a weak influence on stereoselectivity at room temperature and led to a slight increase of the α -D-anomer at −80°.
16 citations
TL;DR: The solid-state structures of C12 bola form isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key intermolecular interactions between bolaform headgroups are necessary to determine the structure in the solid state.
Abstract: Glycal-based bolaforms serve as synthetically flexible components of molecular self-assembly. The compounds are prepared in good yield by a Ferrier reaction between triacetylglucal or -galactal or diacetylxylal and a long chain α,ω-diol, followed by deacetylation under Zemplen conditions. The reactions are stereoselective and preferentially afford the α-diastereomer. The bolaforms undergo self-assembly in water or water/dioxane solution to give a variety of nanostructures. In solution, bolaforms with C8 or C10 chains between glucal headgroups form nanoscale vesicles. In contrast, bolaforms with C12 chains exhibit lower solubility and a dynamic self-assembly, forming several different nanoscale structures. However, the solid-state structures of C12 bolaform isomers adopt shapes very similar to those of bolaforms possessing more extensive hydrogen-bonding networks, indicating that multiple hydrogen bonds in solution are important to formation of stable, discrete nanostructures but that only a few key interm...
16 citations
TL;DR: A nonclassical, totally stereoselective synthesis of orthogonally protected 1,3-disaccharides is reported, which smoothly gave the corresponding 2,2'-dideoxydisaccharide.
Abstract: A nonclassical, totally stereoselective synthesis of orthogonally protected 1,3-disaccharides is reported. Enantiomerically pure beta-keto-delta-lactones, efficiently obtained from glucal and galactal, are transformed into electron-poor heterodienes and chemo-, regio-, and stereoselectively cycloadded to glycals as electron-rich dienophiles, to directly afford 2-thiodisaccharides. The reductive desulfurization of the latter smoothly gave the corresponding 2,2'-dideoxydisaccharides.
16 citations
TL;DR: In this article, a search for appropriate reaction conditions for the equimolar methoxymercuration of D -glucal triacetate was made by using various mercuric salts, bases, and reaction solvents.
16 citations
TL;DR: Scandium(III) trifluoromethanesulfonate was found to catalyze efficiently the O-glycosidation of 3,4,6-tri-O-acetyl-d-glucal with various alcohols and phenols to afford the corresponding 2,3-unsaturated glycosides in excellent yields with good anomeric selectivity as discussed by the authors.
Abstract: Scandium(III) trifluoromethanesulfonate is found to catalyze efficiently the O-glycosidation of 3,4,6-tri-O-acetyl-d-glucal with various alcohols and phenols to afford the corresponding 2,3-unsaturated glycosides in excellent yields with good anomeric selectivity.
15 citations