Use of selenium in carbohydrate chemistry: Preparation of C-glycoside congeners

Synthesis of Methoxy‐Substituted Exocyclic (E)‐ and (Z)‐Unsaturated Methyl Pyranosides and a Study of Their Reactivity towards Lewis Acids

“…Such a behaviour has previously been observed. [24] Davis' reagent, [25] known to perform an oxidation without the release of a nucleophile, was then used [26] in the presence of vinyl acetate to trap the released PhSeOH, [15] thus affording the methoxy-substituted exocyclic derivatives 10 and 11 in 30 and 50% yield, from the acetals 8 and 9, respectively (Scheme 4). Finally, the use of Ti(OiPr) 4 and tBuOOH [24,27] in the presence of anhydrous triethylamine, proved to be the best conditions and gave the methoxysubstituted exocyclic derivatives 10 and 11 in 60 and 77% yield from 8 and 9, respectively (Scheme 4).…”

“…The difficulty associated with the synthesis of such compounds has already been underlined by Jones and Scott in their synthesis of 3: [12] ''The oxyglycal 3 ... represents a new class of acetal-protected oxyglycals, which is unavailable by classic methods.'' In carbohydrate chemistry, mixed O,Seacetals have previously been utilized to synthesise endo- [14] and exocyclic unsaturated derivatives [15] as well as oxy-substituted endocyclic unsaturated derivatives. [16] We therefore explored this option to provide an entry, so far unknown, to alkoxy-substituted exocyclic unsaturated derivatives.…”

Design and Synthesis of a Cyclopentene Scaffold Mimicking Oseltamivir as a Novel Neuraminidase Inhibitor

“…Diphenylphosphorylazide (2.42 mL, 11.2 mmol) was added dropwise to a solution of 9 (1.13 g, 2.24 mmol), triphenylphosphine (2.94 g, 11.2 mmol), and DEAD (1.77 Ml, 11. (4R,5R)-5,6-(Tetraisopropyldisiloxane-1,3-diyl)-4-acetamido-3-benzoyloxymethyl-1-cyclopentene (11). Water (0.03 mL, 1.34 mmol) and tripheylphosphine (0.44 g, 1.68…”

The Wittig-cyclization procedure: acid promoted intramolecular formation of 3-C-branched-chain 3,6-anhydro furano sugars via 2′-oxopropylene derivatives

“…5 When unstabilized ylides are used for the formation of Wittig products, cyclization can be obtained by halo-, seleno-or mercuri-electrophilic activation. [9][10][11][12] Stereoselective routes for the C-a-and C-b-glycosyl compounds have also been reported by the use of promoters such as zinc powder 13 and iodine. 14 Sugar lactones have also been converted to C-glycosides using the Wittig-cyclization method.…”

“…1 The Wittig approach has been widely used in ring-closure reactions of both furanose and pyranose derivatives, to produce C-glycosides. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] However, formation of anhydrosugar derivatives other than C-glycosides have not been widely studied especially under acidic conditions. Ethoxycarbonylmethylene derivatives of sugars have probably been the most widely used, ring-closures having been carried out under weakly basic conditions (Moffatt Cglycosidation).…”