Glucofuranose, 1,6-anhydro

Fourteen DFAs and some oligomers were identified in caramel obtained by thermal treatment of inufin. - Monosaccharides (glucose, fructose), dehydration products (1,6-anhydro-p-D-glucopyranose, 1,6-anhydro-p-D-glucofuranose), disaccharides (gentiobiose and isomaltose), and oligosaccharides were also found in glucose and sucrose caramel. ... 

If the disposition of hydroxyl groups is such that either an ethylene oxide or a hydrofuranol ring could be formed, then it is the three-membered anhydro ring that is preferentially established. Thus, if 6-tosyl-isopropylidene-D-glucofuranose (XII), in which there are present free hydroxyls at C3 and C5, is submitted to alkaline hydrolysis, it is the 5,6-anhydride VI alone that is formed7 the 3,6-anhydride appears only if the hydroxyl at C5 is protected by substitution as in X. 

Some examples will illustrate the applicability of this generalization in so far as it concerns alkaline scission. 5,6-Anhydro-l,2-isopropylidene-D-glucofuranose with alcoholic sodium hydroxide gives a mixture of isopropylidene-D-glucose and isopropylidene-L-idose. The latter results from inversion on C5, the former presumably by inversion on the non-asymmetric C6.7 3,4-Anhydro-l,2-isopropylidene-D-psicose (or allu-lose17) (XX) when treated with sodium hydroxide yields a mixture of products among which 1,2-isopropylidene-D-fructose (XIX) was detected (in the representations inversions are denoted by circles above the arrows and the carbons inverted are noted below the arrows). With sodium methoxide, however, l,2-isopropylidene-4-methyl-D-sorbose (XXI) is the chief product and results from inversion on C4.1S... 

Another example is provided by the observation of Ohle and Wilcke16 that whereas 3-tosyl-l,2-isopropylidene-D-glucofuranose (XXXV) is saponified without anhydro ring formation and without Walden inversion, the triacetate of methyl 3-tosyl-/3-D-glucofuranoside (XXXVI) is... 

It is to be expected, on these grounds, that the predominating component of the mutarotation equilibrium of 3,6-anhydro-glucose will be 3,6-anhydro-glucofuranose whereas that of 3,6-anhydro-galactose will be the open-chain form. Neither will include pyranose forms. 

Soltzberg, Goepp and Freudenberg10 proved the constitution of arlitan by a synthetic method. They obtained a liquid tetramethyl derivative of arlitan, characterized it by its boiling point, density and refractive index, and compared it with 2,3,5,6-tetramethyl-l,4-anhydro-D-sorbitol (V) synthesized by the following method. Tetramethyl-D-glucofuranose... 

The 5,6-anhydro derivatives of D-sorbitol and D-mannitol41 69 behave in like manner to the 5,6-anhydro-l,2-isopropylidene-D-glucofuranose of Freudenberg and coworkers.70 Thus, 5,6-anhydro-l,3 2,4-diethyli-dene-D-sorbitol (LXXXV) readily suffers ring scission with ammonia to give 6-amino 6-desoxy-l,3 2,4-diethylidene-D-sorbitol (LXXXVI)69 or with sodium methoxide to form 6-methyl-l,3 2,4-diethylidene-D-sorbitol.42 l,2 3,4-Diisopropylidene-5,6-anhydro-D-mannitol gives rise... 

Der Mechanismus der Pyrolyse soil ahnlich wie bei der sauren Glykosid-Spaltung sein 26,70,78,153) die Ausbeuten reichen bis zu 25% bei Starke und bis zu 70% bei Cellulose. Bei der Pyrolyse entstehen auBer der 1,6-Anhydro-p-D-glucopyranose die entsprechende 1,6-An-hydro-D-glucofuranose 55,70,75,76,230) ud femer 1,6-3,4-Dianhydroderi-vate sowie Derivate des Furans, welche gaschromatographisch nachge-wiesen werden konnen... 

A third strategy was applied to the synthesis of a neighboring family of amphiphilic carbohydrates. The starting material was 5,6-anhydro-l,2-0-iso-propylidene-a-D-glucofuranose, easily obtained in a few steps from o-glucose. The latter was reacted with M-benzyl-n-hexadecylamine to afford regioselec-tively the 6-alkylamino-6-deoxy compound 35 [ 119]. 

SE-52 at 160°. Similarly, l,6-anhydro-/ -D-glucofuranose corresponds to /J-D-xylopyranose. These anhydro compounds must be formed in the acid-hydrolysis stage, and they give incorrect values for D-xylose unless their presence is detected 78 this may be done by operating the column at 135°. 

In conformationally mobile systems in which the required antl-periplanar arrangement is readily achieved (even though this may not be the favored conformation), the reaction is usually complete within hours at 0-25°, or after a few minutes at the reflux temperature. Thus, l,2-0-isopropylidene-6-0-p-tolylsulfonyl-a-D-glucofuranose (I) affords 5,6-anhydro-l,2-0-isopropylidene-a-D-glucofuranose (2) within... 

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