Reaktion von 2,3,4-tri-O-acetyl-1,6-anhydro-β-D-glucopyranose mit as.-Dihalogenmethyläther

Bognŕ, R.; Farkas, I.; Menyhart, M.; Groß, H.; Paulsen, Hans

doi:10.1016/s0008-6215(00)81234-3

Cited by 11 publications

(1 citation statement)

References 4 publications

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“…5 The resulting products are generally useful starting materials for a variety of syntheses. [1][2][3][4][5][6][7] Locked in the 1 C 4 conformation, such 1,6-anhydrohexopyranoses are quite rigid structures which offer special advantage for the stereoselective introduction of functional groups at carbohydrate ring positions 2 to 4 while the 1-and 6-hydroxy functions are protected by the anhydro bridge. The 1,6-anhydro bridge is stable in basic media, but is cleaved readily under acidic aqueous conditions.…”

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confidence: 99%

Reactions of 2-Hydroxy-6,8-dioxabicyclo[3.2.1]oct-3-ene with Diethylaminosulfur Trifluoride and with Halogens. Facile Synthesis of 1,6-Anhydrohalohexopyranoses

Oberdorfer¹,

Haeckel²,

Lauer³

1998

Synthesis

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D-Galactal 1 reacts in THF in the presence of catalytic amounts of concentrated sulfuric acid to give (2R)-2-hydroxy-6,8dioxabicyclo[3.2.1]oct-3-ene (4) in a Ferrier-type rearrangement in 40% yield. When 4 is treated with diethylaminosulfur trifluoride (DAST) under certain reaction conditions, a novel intramolecular second order allylic rearrangement follows leading to previously unknown diastereomeric monofluoro derivatives 7 and 8. Direct asubstitution of 4 by DAST affords the 2-monofluoro derivative 6 under kinetic control. When DAST is used with dimethylformamide as solvent an apparent [1,3] sigmatropic migration of the 2-hydroxy group of 4 gives (4S)-4-hydroxy-6,8-dioxabicyclo[3.2.1]oct-2-ene (9). The corresponding 4-fluoro-substituted product was not obtained from the reaction of 9 with DAST. Oxidation of 4 and repeated treatment with DAST gives a novel 2,2-difluoro compound 11. Electrophilic addition of bromine to protected 4 afforded the 1,6anhydromonobromo-and-dibromohexopyranoses 15-17. Monohalo and monopseudohalo derivatives (-F,-Cl,-Br,-N 3) 22-25 were prepared by nucleophilic oxirane ring opening of the easily available endo-epoxides 18-20.

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confidence: 99%