- Direct conversion of 1-deoxy-1-nitroalditols to methyl glycofuranosides
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Treatment of the sodium nitronate forms of 1-deoxy-1-nitrohexitols with methanolic sulfuric or hydrochloric acid at -30 °C leads to their regiospecific conversion to the corresponding methyl glycofuranosides. The reaction exhibits more pronounced stereoselectivity for 1-deoxy-1-nitroalditols with the 2,3-erythro configuration than with the 2,3-threo substrates and cis methyl glycofuranosides are the major products. The observed stereoselectivity indicates the lysis of the protonated aci-nitro form which is a two-step process consisting of nucleophilic addition to the protonated carbon-nitrogen double bond followed by the bimolecular nucleophilic substitution of the nitrogen-containing residue.
- Vojtech,Petru?ová,Pribulová,Petru?
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p. 3112 - 3116
(2008/09/20)
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- A convenient synthesis of D-idose
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Addition of nitromethane to D-xylose leads to the formation of two epimeric deoxynitroalditols, namely 1-deoxy-1-nitro-D-iditol and 6-deoxy-6- nitro-L-glucitol. Conversion of the former, obtainable in good yield by direct crystallisation, by a modified Nef reaction in an argon atmosphere afforded 68% of D-idose, which may readily be converted into 1,6-anhydro-β- D-idopyranose ('D-idosan').
- Dromowicz, Manfred,Koell, Peter
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p. 169 - 171
(2007/10/03)
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- Addition of Nitromethane to Aldoses. - A Comprehensive Study of the Diastereoselectivity of the Fischer-Sowden Reaction by Help of 13C-NMR Spectroscopy
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The addition of nitromethane to aldoses, commonly referred to as "Fischer-Sowden reaction", is not as stereoselective as can be concluded from the literature.This is the outcome of a comprehensive study which covered besides glyceraldehyde all aldotetroses, -pentoses and -hexoses.The ratio of the pair of diastereomeric nitroalditols has been determined in each case by 13C-NMR spectroscopy.Thus, incidentially, a whole set of spectral data for all tetritols, pentitols, hexitols and heptitols with a terminal nitro group has been obtained, which can be correlated systematically to the respective data for the parent alditols.From these results follows that at least under conditions which give high yields of products, the reaction is thermodynamically controlled; thus, the product ratio is determined by the different energy content of the product nitroalditols (or their nitronates), which is a result of different patterns of steric interactions between substituents.
- Koell, Peter,Stenns, Claudia,Seelhorst, Willi,Brandenburg, Heinz
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p. 201 - 206
(2007/10/02)
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