Idose, 3,6-anhydro

Idose, 3,6-anhydro-L-, 52 Inositol, aminodeoxy-meso-, 53 Inulin, 306... 

When heated to 100 CC/ D-idose undergoes a reversible loss of water and exists primarily as 1,6-anhydro-n-idopyranose. 

The identification of L-iduronic acid as the major glycuronic acid constituent of heparin proved to be a much slower process than the identification of the amino sugar residue. Although this compound was detected in acid hydrolyzates of heparin116117 and heparin oligosaccharides,118 its yield was usually poor, because of the drastic conditions used for the acid hydrolysis (which are known to lead to extensive destruction of uronic acid).119120 Also, L-iduronic acid escaped detection as L-idose in the hydrolyzates of carboxyl-reduced heparin, probably because L-idose is readily converted into 1,6-anhydro-L-idose under the usual hydrolytic conditions. 

Examination of early -n.m.r. spectra of heparin and of chemically modified heparins121 prompted a reinvestigation of N,0-desulfated, carboxyl-reduced heparin, leading to the isolation of substantial amounts of L-iditol pentaacetate.121,122 In addition, improved conditions for the acid hydrolysis of heparin and carboxyl-reduced heparin gave increased recoveries of L-iduronic acid and 1,6-anhydro-L-idose, respectively.123 These findings confirmed the L-enantiomeric designation of the iduronic acid, and established that it is the main uronic acid in heparin. 

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... 

As a further illustration of the scope for use of 1,6-anhydro sugars in the preparation of uncommon sugars, the rare L-idose derivative 210 has been prepared recently and used in the preparation of oligosaccharides containing iduronic acid... 

A. C. Richardson and H. O. L. Fischer, Cyclization of dialdehydes with nitromethane, Part VI. Preparation of 3- amino-1,6-anhydro-3-deoxy-p-D-gulose, -P-D-altrose and -p-D-idose derivatives and their characterization by means of inversion of mesyloxy groups,./. Am. Chem. Soc., 83 (1961) 1132-1139. 

Anhydro-L-idose is reported to form 5-(hydroxymethyl)-2-furalde-hyde (5) several hundred times faster than D-glucose forms it.21 As with... 

Neighboring-group participation by the vicinal, trans-acetoxyl group (see p. 125) serves to explain the abnormal behavior of methyl 4-0-acetyl-2,3-anhydro-6-0-benzyl- or -trityl-a-D-gulopyranoside with hydrogen chloride in acetone, or with 80% aqueous acetic acid, which give D-galactose, instead of the D-idose, derivatives.67 In the same way, 2-0-acetyl-3,4-anhydro-D-altropyranosides yield D-man-nosides, not D-idosides.9 6z(see p. 125). 

Hydrolysis of 5,6-anhydro-l,2-0-isopropylidene-a-D-glucofuranose with sodium hydroxide under controlled conditions can lead71-74 to both 3,5-anhydro-l,2-0-isopropylidene-/3-L-idofuranose and 3,6-anhydro-l,2-0-isopropylidene-a-D-glucofuranose, in addition to 1,2-O-isopropylidene-a-D-glucofuranose (see p. 130), whereas mild hydrolysis with 5 mM sulfuric acid can give up to 25% of 2,5-anhydro-L-idose (62), besides the expected D-glucose.195 This reaction must in-... 

A reaction identical from the standpoint of mechanism is the conversion81 of 3-0-benzyl-l,2-0-isopropylidene-5,6-di-0-p-tolyl-sulfonyl-D-glucofuranose (68) into 2,5-anhydro-3-0-benzyl-6-0-p-tolylsulfonyl-L-idose dimethyl acetal (70) by boiling a solution of 68 in methanol containing 2% of concentrated hydrochloric acid for 40 hours under reflux. These two reactions involve initial removal... 

It should be noted that 2,5-anhydro-aWe/ryt/o-L-idose (79) had already been obtained85 by the action of aqueous sulfuric acid on 5,6-anhydro-l,2-0-isopropylidene-a-D-glucofuranose (76) anhydride 79 is formed in 25% yield, together with D-glucose (80), which is the major product (60%) in the reaction. 

A new synthesis of 2,5-anhydro-L-iditol was achieved49 by reduction of 2,5-anhydro-L-idose with sodium borohydride. The product was identified as its crystalline l,6-bis(p-toluenesulfonate), which was already known.1... 

The L-idose derivative 98 gave a small proportion of the substitution product, and an attempt to improve its yield by protecting the 3-hydroxyl group by acetylation surprisingly did not prevent formation of the 3,6-anhydro ring, the substitution product being formed only in low yield. The D-glucose isomer of 98 could not be converted by... 

The difference between the behavior of the 6-amino-6-deoxy-D-glucose and -L-idose derivatives can be rationalized as follows. In the transition states for the formation of the 3,6-anhydro ring from the Tt-gluco isomers, the oxygen (or hetero) atoms attached to C-4 and C-5 are in a sterically unfavorable, cis relationship. The transition states from the h-ido amines involve a trans relationship of these hetero atoms. Thus, for the D-gluco amine, deamination reactions other than 3,6-anhydro ring-formation compete more effectively. 

O-Isopropylidene-l,0-di-O-tosyl-D-fructose 6-Deoxy-2,3-0-isopropyIidene-l-0-tosyl-D-fructose 5,6-Anhydro-l,2-0-isopropyIidene-3-0-tosyl-L-idose... 

In relation to these solvolyses is the formation of free 2,5-anhydro-L-idose upon attempted hydrolysis of 5,6-anhydro-1,2-O-isopropylidene-a-D-gluco-furanose.364... 

J. Defaye and V. Ratovelomanana, Solvolyse d esters sulfoniques dans la serie du glucofuranose. Acces aux derives du 2,5-anhydro-L-idose et du 2,5-anhydro-L-iditol, Carbohydr. Res., 17 (1971) 57-65. 

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