Anhydrosugar acetals

O-stannylene acetals,84 glycals and 1,2-anhydrosugars,85 and to selective de-O-benzylation of position-2 with TIBAL, DIBAL-H57 or Lewis acid catalysts,86 or to the one-pot access to 3-O-benzyl-4,6-0-benzylidene glucosides by tandem catalysis recently reported.87 The 1,2-lactones recently reported by Linker and co-workers35 are also synthons which provide... 

Polymerization of bicyclic acetal (1,4-anhydrosugar) composed of fused 5- and 6-membered rings may involve opening of both rings, because a 6-membered ring exists in enforced unfavorable boat conformation [150-152] ... 

Figure 7.2.1. Cellulose pyrolysate obtained at 59CP C and trimethylsilylated. The separation was done on a methyl silicone with 5% phenyl silicone type column. 1 1,2-dihydroxyethane, 2 2-hydroxypropionic (lactic) acid, 3 hydroxy acetic (glycolic) acid, 4 turanmethanol, 5 peak from silylation reagents, 6 1,3-dihydroxypropanone, 7 1,4-dioxane-2,5-diol, 8 1,3-dioxolane-4,5-diol, 9 1,3-dihydroxybenzene, 10 2-methyl-1,4-dioxane-2,5-diol, 11 1,4-dihydroxybenzene, 12 3-hydroxy-2-(hydroxymethyl)-2-cyclopenten-1-one, 13 2-hydroxy-5-(hydroxymethyl)-4(H)-pyran-4-one, 14 1,2,3-trihydroxybenzene, 15 internal standard, 16 an anhydrosugar, 17 levoglucosan (1,6-anhydro-p-D-glucopyranose), 18 a monosaccharide, 19 an anhydrosugar, 20 an anhydrosugar, 21 1.6-anhydro-P-D-glucofuranose .

Acetolysis of the anhydrosugar 118 gave a mixture of pyranosyl and furanosyl glycosyl acetates, which could be converted to the 3 -hydroxymethyl nucleosides 119 and, after a deacetylation-periodate-borohydride sequence, 120 respectively. ... 

Alkylideneaceto-acetic esters Allylumlagerung Allyl rearrangement Ameisensaure Formic acid Amldosulfonsaure Sulfamic acid Anhydrozucker Anhydrosugars Anlagerung Addition Arylierung Arylation Asparaginsauren Aspartic acids Aufbau Synthesis Austausdi Replacement Benzopersaure... 

Water analysis of liquids was by Karl Fischer titration. Liquids were analyzed by GC for qualitative or semi-quantitative characterization. Quantitative analysis of selected liquid components was performed by HPLC. The sample was prepared by diluting it with two parts water to cause phase separation of pyrolytic lignin. Simple sugars, anhydrosugars, and other lower molecular weight components such as acetic acid and hydroxyacetaldehyde remain in the aqueous phase. 

The bicyclic acetal, 6,8-DBO, possesses the structural skeleton of the 1,6-anhydrosugars and, because it is readily prepared from acrolein dimer, its cationic polymerization has been investigated. Mostly Lewis acids (BF3, PF5) were used as initiators, and at low temperature (-78 °C) polymers with Mn up to 10 could be obtained although dispersity was broad. ... 

Scheme 26 Skeletons of typical anhydrosugars containing acetal bonds.

The rationalization of the formation of this unexpected product is shown in Figure 10.32. Removal of the acetate group from the Cl position under the basic conditions provided hemiacetal 98a, which is in equilibrium with aldehyde alcohol 98b. Reduction of 98a yields the expected triol 94a. However, there is a possibility of the attack of the oxy-anion from the C-5 position at the C3 center with the elimination of benzyl alcohol. The resulting oxetane 99 is then opened by the primary alkoxylate (formed after reduction of the carbonyl group), providing finally the anhydrosugar... 

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