An alternative route to furanoid and pyranoid glycals

Rapid Preparation of Variously Protected Glycals Using Titanium(III)

“…Treating a 2,3-cyclic acetal derivative with 1 gives the free allylic alcohol-substituted glycal by acetal ring fragmentation. [17][18][19]22,24 Reaction of 2,3:4,6-di-O-isopropylidenemannopyranosyl bromide 56 with 1 gave 4,6-O-isopropylidene glucal 9 (Scheme 2).…”

“…The mixture was concentrated and washed (saturated aqueous NaHCO 3). The organic fractions were dried (MgSO4), concentrated, and purified by preparatory TLC (1:1 hexanes/ethyl acetate) to give the title compound as a mixture of R-and -anomers: 19 …”

Synthesis of Pyranoid and Furanoid Glycals from Glycosyl Sulfoxides by Treatment with Organolithium Reagents

“…It has been suggested that heterolytic cleavage of the carbon-halogen bond occurs under these acidic conditions, initially to give an anomeric carbocation that, after taking two electrons from the zinc atom, generates a transient carbanion that evolves through the splitting off of an acetate anion. [10] Other reducing agents used in this transformation with glycosyl halides include sodium and potassium metal, [11] sodium naphthalide, [11] zinc/silver graphite, [12] aluminum amalgam, [13] SmI 2 , [14] potassium graphite, [15] lithium/ammonia, [16] chromium(II), [17,18] zinc/base, [19] cobalt(II), [20] and titanium(III). [21] A glucal derivative has also been prepared by introduction of a halogen atom at C-2, followed by a reductive elimination reaction in the opposite sense.…”

Polymerization of Unsaturated Sugars I. Radical Copolymerization of D-Glucal Derivatives and Maleic Anhydride

“…This made difficult the determination of the equilibrium constant K for complex formation. The constant K was thus determined according to the method used by Foster and Fyfe 14 where the chemical shifts of the donor molecules in the 13 Table I the intercepts of the lines are positive seem to indicate the formation of contact chargetransfer complexes.…”

“…Charge-Transfer Complex Formation The association constant K was determined by 13 C NMR spectroscopy as reported by Foster and Fyfe. 14 The NMR spectra were measured in CDC1 3 at 25°C at the following monomer concentrations:…”