- The Reaction of N-Dichloromethylene-N,N-dimethylammonium Chloride (Viehe's Salt) with Some Carbohydrate Diols
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The reaction of Viehe's salt (Me2N1+=CCl2Cl1-) with various carbohydrate diols (manno, allo) in the presence of a base is reported, the products being, after hydrolysis, either carbonate (with pyridine) or the carbamate (with triethylamine).A rationalization of the two different types of product formed is given in terms of the stereoelectronic control proposal by Deslongchamps.
- Copeland, Christopher,Stick, Robert V.
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p. 581 - 589
(2007/10/02)
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- PRACTICAL SYNTHESIS OF O-β-D-MANNOPYRANOSYL-, O-α-D-MANNOPYRANOSYL-, AND O-β-D-GLUCOPYRANOSYL-(1->4)-O-α-L-RHAMNOPYRANOSYL-(1->3)-D-GALACTOSES
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The Koenigs-Knorr glycosylation of 4,6-O-ethylidene-1,2-O-isopropylidene-3-O-(2,3-O-isopropylidene-α-L-rhamnopyranosyl)-α-D-galactopyranose (3) by 4,6-di-O-acetyl-2,3-O-carbonyl-α-D-mannopyranosyl bromide (10), as well as Helferich glycosylations of 3 by tetra-O-acetyl-α-D-mannopyranosyl and -α-D-glucopyranosyl bromides, proceeded smoothly to give high yields of trisaccharide derivatives (12, 16, and 17).An efficient procedure for the transformation of 12, 16, and 17 into the α-deca-acetates of the respective trisaccharides has been developed.Zemplen deacetylation then afforded the title trisaccharides in yields of 53, 52, and 62percent respectively, from 3.A new route to 1,4,6-tri-O-acetyl-2,3-O-carbonyl-α-D-mannopyranose is suggested.
- Betaneli, Vitali I.,Ovchinnikov, Michael V.,Backinowsky, Leon V.,Kochetkov, Nikolay K.
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p. 211 - 224
(2007/10/02)
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- The Reaction of Methyl 4,6-O-Isopropylidene-2,3-O-thiocarbonyl-α-D-mannoside with Methyl Iodide: a Synthesis of Methyl α-Tyveloside (Methyl 3,6-Dideoxy-α-D-arabino-hexopyranoside)
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The reaction of methyl 4,6-O-isopropylidene-2,3-O-thiocarbonyl-α-D-mannoside with methyl iodide gives two major products, methyl 3,6-dideoxy-3,6-diiodo-2-O-(methylthio)carbonyl-α-D-altropyranoside and methyl 2,3-O-carbonyl-6-deoxy-6-iodo-α-D-mannopyranoside, both of which lack the 4,6-O-isopropylidene grouping but contain the 6-deoxy-6-iodo function, and another minor product.One of the major product, methyl 3,6-dideoxy-3,6-diiodo-2-O-(methylthio)carbonyl-α-D-altropyranoside, is convertedinto methyl α-tyveloside by sequential reduction and ester removal.The incorporation of iodine at C 6 is seemingly due to hydrogen iodide, and may be suppressed in the presence of N,N,N,N-trtramethylnaphthalene-1,8-diamine or propylene oxide, or by the use of 4,6-O-benzylidene-2,3-O-thiocarbonyl-α-D-mannoside as substrate.Methyl iodide/propylene oxide is apparently an efficient combination for thiocarbonate (C=S) into carbonate conversion.The structure of the minor product was shown by single-crystal X-ray diffraction to be 1,6-anhydro-3-deoxy-3-iodo-2-O-(methylthio)carbonyl-β-D-altropyranose.
- Patroni, Joseph J.,Skelton, Brian W.,Stick, Robert V.,White, Allan H.
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p. 987 - 999
(2007/10/02)
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