Pyranose

About: Pyranose is a research topic. Over the lifetime, 1619 publications have been published within this topic receiving 35348 citations. The topic is also known as: pyranoses & hexopyranose.

Thio-Sugars III. Radical Catalyzed Thione-Thiol Rearrangement of Cyclic Thionocarbonates on a Pyranose Ring : Formation of cis-Arranged Cyclic Thiolcarbonates

Abstract: Pyranoside 3, 4-cis-thionocarbonates, under radical-promoted reaction conditions (method A, B, or C, described in the text), gave O-S rearrangement products, 3, 4-thiolcarbonates of cis-stereochemistry, in accepTable yields.2, 3-Thionocarbonates of trans-stereochemistry also gave the rearrangement products of cis-stereochemistry preferentially in method B (photolysis with hexabutyldistannane). Although regio-control of the product was not satisfactory in most cases, some of the results suggested that the regioselectivity of the reaction is markedly influenced by the stereochemistry of the anomeric position of the substrates. The products were converted to thioglycosides(peracetate forms) by conventional means.

Metal complexes of carbohydrates: isolation and characterisation of cobalt(III) complexes containing N-substituted glycosylamine ligands derived from ethane-1,2-diamine and glucosamine

Abstract: Reaction between cis- or trans-[Co(en)2CI2]+(en = ethane-1,2-diamine) and D-glucosamine (2-amino-2-deoxy-D-glucopyranose) in neutral aqueous solution results in a very complicated product mixture including as a major component several isomeric complex ions in which the co-ordination sphere is formally made up of two ethane-1,2-diamine units and one sugar unit. Separation of these complexes by ion-exchange chromatography, and subsequent spectroscopic and structural studies have shown that they are diastereomeric forms in which the co-ordination sphere actually contains one bidentate ethane-1,2-diamine chelate and a multidentate ligand which is an N-(2′-aminoethyl)amino-substituted glycosylamine derived from glucosamine, fructosamine or mannosamine. The presence of the fructosamine moiety reveals that the complex formation reaction is accompanied by the Amadori rearrangement of glucosamine, while the presence of the mannosamine moiety indicates that this rearrangement may be reversible and possibly stereospecific in particular diastereoisomers. Crystal structure determinations have definitively characterised eight of the reaction products as: 1 a complex of the 1-N-(2′-aminoethyl)amino-substituted glucosamine in which the sugar, although chelated to the metal as part of a tridentate ligand, is in its open-chain form and in which the four nitrogen atoms derived from the original two ethane-1,2-diamine units are essentially coplanar; 2 a complex of tridentate 1-N-(2′-aminoethyl)amino-substituted glucosamine in which the sugar has its pyranose form and the chelate edges spanned by the original ethane-1,2-diamine units are in the Δ configuration; 3 a complex of 1-N-(2′-aminoethyl)amino-substituted glucosamine in which the sugar is in its open-chain form and the ligand is bound in a quadridentate manner, with the chelate edges spanned by the original ethane-1,2-diamine units in the Δ configuration; 4 a complex of 1-N-(2′-aminoethyl)amino-substituted mannosamine in which the sugar has a furanose form and is part of a quadridentate ligand, and the chelate edges spanned by the original ethane-1,2-diamine units are in the Δ configuration; 5 a complex of quadridentate 1-(2′-aminoethylamino)-1-deoxy-fructopyranosylamine in which the chelate edges spanned by the original ethane-1,2-diamine units are in the Δ configuration; 6 a complex of quadridentate 1-(2′-aminoethylamino)-1-deoxy-fructopyranosylamine in which the chelate edges spanned by the original ethane-1,2-diamine units are in the Δ configuration; 7 the same complex as 6 but in the form where its co-ordinated sugar hydroxyl group is deprotonated; and 8 a complex of 1-(2′-aminoethylamino)-1-deoxyfructopyranosylamine in which the chelate edges spanned by the original ethane-1,2-diamine units are in the Δ configuration.

The Deoxygenation of Some Carbohydrate Diols Via the Derived Cyclic Thiocarbonate

Abstract: The treatment of methyl 2,6-di-O-methyl-3,4-O-thiocarbonyl-β-D-galactoside with methyl iodide gives mainly the 3-deoxy-3-iodo-D-guloside , whereas the α- anomer of the above and methyl 2-O-methyl-3,4- O- thiocarbonyl-β-L-arabinoside give mainly the 4-deoxy-4-iodo-D- glycosides. An explanation is given for these and some previously reported results. As well, two of the above cyclic thiocarbonates (β-D-galacto and β-L- arabino), together with two cyclic thiocarbonates derived from methyl α-D- mannopyranoside, when treated with tributyltin hydride, gave mixtures (nearly 1:1) of products resulting from deoxygenation . Single-crystal X-ray diffraction structure determination of the β-D- galacto and the β-L- arabino cyclic thiocarbonates showed both pyranose rings to be in the 4C1 conformation.