909. Ionophoresis of carbohydrates. Part VII. 2,5-Di-O-methyl-L-rhamnose: its ionophoresis and conversion into 6-deoxy-2,5-di-O-methyl-L-altrose

Synthesis of l-Hexoses

“…This can be accomplished by nucleophilic displacement of sulfonates with inversion of stereochemistry. − In an early report by Jones and Nicholson 2- O -tosyl- l -fucoside 547 was heated in aqueous hydrochloric acid resulting in the formation of 6-deoxy- l -taloside 548 (Scheme a) . Methyl 2,5-di- O -methyl-α- l -rhamnofuranoside has also been converted by treatment with sodium benzoate to afford the l -altrofuranoside . Hasegawa and co-workers also explored the preparation of various 6-deoxy- l -hexoses from l -fucose and l -rhamnose via substitutions of the corresponding triflate .…”

“…420 Methyl 2,5-di-Omethyl-α-L-rhamnofuranoside has also been converted by treatment with sodium benzoate to afford the L-altrofurano-side. 421 Hasegawa and co-workers also explored the preparation of various 6-deoxy-L-hexoses from L-fucose and L-rhamnose via substitutions of the corresponding triflate. 422 The substitution was affected by reacting 3-O-triflate L-fucoside 549 with CsOAc in the presence of crown ether, affording 6-deoxy-L-guloside 550 (Scheme 83b).…”

Rules and Stereoelectronic Guidelines for the Anionic Nucleophilic Displacement of Furanoside and Furanose O-Sulfonates

“…(b) S N 2 displacements on β­(1,4)-α­(2,3)-O3-tosylates and mesylates ,, and β(1)-α­(2,3,4)-O3-tosylates and mesylates generally proceed in acceptable yield (eqs , 22) …”

Stereoselective Synthesis and Determination of the Cytotoxic Properties of Spicigerolide and Three of Its Stereoisomers

“…The selective manipulation of the aldehyde function of the rhamnose moiety required the introduction of protecting groups into the polyhydroxylated chain . The starting compound was the known thioacetal 8 (Scheme ), easily prepared in two steps and 83% overall yield from l -rhamnose . Silylation of diol 8 to compound 9 was performed with tert -butyldimethylsilyl triflate .…”