Synthesis of carbohydrate derivatives containing vinylic thioether groups 1

Abstract

The reaction of methyl 4,6- O-benzylidene-3- O-(methylsulfonyl)-2- S-phenyl-2-thio-α- D-altropyranoside ( 3) with 1,5-diazabicyclononene in methyl sulfoxide affords the corresponding 2-vinyl thioether 4 in high yield. Reaction of the isomeric 3-phenylthio-2-methanesulfonate 11 under the same conditions affords methyl 4,6- O-benzylidene-2,3-dideoxy-α- D- erythro-hex-2-enopyranoside ( 5) with elimination of both substituents. With sodium hydride in dimethoxyethane 11 gives the expected vinyl thioether 12 in which the phenylthio substituent is at C-3. These base-catalyzed elimination reactions in methyl 4,6- O-benzylidene-α- D-altropyranosides containing diaxial phenylthio and methylsulfonyl substituents appear to be highly dependent on the location of substituents and the solvent. Under the same experimental conditions, the 3-phenylthio-2-methanesulfonate system behaves markedly differently from the conformationally and configurationally related 2-phenylthio-3-methanesulfonate system. Elimination is also effected with 1,2- O-isopropylidene-3,5-di- O-(methylsulfonyl)-6- S-phenyl-6-thio-α- D-glucofuranose ( 18), which gives the corresponding 6-phenylthio-5,6-ene derivative ( 19).