title: A new 6-C-alkylation from an alkyl mannofuranoside 5,6-cyclic sulfate.
abstract: Methyl 6-C-alkyl-6-deoxy-alpha-D-mannofuranoside derivatives have been synthesized from methyl 2,3-O-isopropylidene-5,6-O-sulfuryl-alpha-D-mannofuranoside (1). In a Path A, reaction of the 5,6-cyclic sulfate 1 with 2-lithio-1,3-dithiane afforded 2-(methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-mannofuranosid-6-yl)-1,3-dith iane (2). Treatment of 2 with n-butyllithium then alkyl iodide gave the corresponding 2-(methyl 5-O-alkyl-6-deoxy-2,3-O-isopropylidene-alpha-D-mannofuranosid-6-yl )-1,3- dithiane. Reaction of 2 with n-butyllithium and 5,6-cyclic sulfate 1 furnished 2-[methyl 6-deoxy-2,3-O-isopropylidene-5-O-(methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-manno-furanosid-6-yl)-alpha-D - mannofuranosid-6-yl]-1,3-dithiane. 2-(Methyl 6-deoxy-2,3-O-isopropylidene-5-O-methyl-alpha-D-mannofuranosid- 6-yl)-1,3-dithiane was converted into the lithiated anion, which after treatment with alkyl halide afforded the corresponding 2-alkyl-C-(methyl 6-deoxy-2,3-O-isopropylidene-5-O-methyl-alpha-D-mannofuranosid-6-y l)-1,3- dithiane. In a Path B, 5,6-cyclic sulfate 1 reacted with 2-alkyl-2-lithio-1,3-dithiane derivatives, which led after acidic hydrolysis to 2-alkyl-2-(methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-mannofuranosid-6-yl)-1,3-dith iane accompanied by methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-lyxo-hexofuranos-5-u loside as the by-product. This methodology was applied to synthesize 2-(methyl 6-deoxy-2,3-O-isopropylidene-5-O-methyl-alpha-D-mannofuranosid-6-y l)-2- (methyl 6-deoxy-2,3-O-isopropylidene-alpha-D-mannofuranosid-6-yl)-1,3-dith iane.
authors.affiliation: Laboratoire de Chimie Organique, Université de Picardie Jules Verne, Amiens, France.
authors.forename: T
authors.initials: T
authors.lastname: Gourlain
authors.forename: A
authors.initials: A
authors.lastname: Wadouachi
authors.forename: D
authors.initials: D
authors.lastname: Beaupère
mesh_terms: D000478:Alkylation; D009682:Magnetic Resonance Spectroscopy; D008362:Mannosides / Q000138:chemical synthesis*; D015394:Molecular Structure; D013431:Sulfates / Q000138:chemical synthesis*
chemical_list: D008362:Mannosides; D013431:Sulfates