L-Idose

Most substrates, with the exception of hydroxypymvate, have a threo configuration of hydroxyl groups at the C-3 and C-4 positions (139). The new stereocenter formed in TK-catalyzed addition is formed in the threo configuration with high diastereo-selectivity (151). Using TK-catalyzed condensations of hydroxypymvic acid with a number of aldehydes a practical preparative synthesis of L-idose [5934-56-5], L-gulose [6027-89-0], 2-deoxy-L-xylohexose, and... 

Problem 25.22 What aldopentose would give a mixture of L-gulose and L-idose on Kiliani-Fischer chain extension ... 

L-idose 293, 311 ff. imine formation 57 imine-enamine tautomerization 467 iminium-RhH jt complex 351 f. imipenem 348 indoline ligands 681, 684 indolizomycin 47 Iff. -.retrosynthetic analysis 472ff. 

Deoxy-5-fluoro-D-glucose and -L-idose were synthesized from 1,2-(9-isopropylidene-a-D-glucofuranurono-6,3-lactone (285). Treatment of l,2-0-isopropylidene-5-0-triflyl-a-D-gluco- (286 prepared from 285) and -) -L-ido-furanurono-6,3-lactones (289 prepared from 288), with BU4NF... 

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... 

The simplified preparations128 of 5-O-sulfonylated derivatives of 1,2-O-isopropylidene-a-D-gIucofuranose (77 and 78) (see Section VI,4) was the key to substantial improvements in the synthesis of L-idose. 

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 nitro group can alternatively be introduced in a sugar by nucleophilic displacement of iodide by a nitrite ion. This procedure was recently used in the preparation of the L-idose derived nitro sugar 14, an intermediate in the synthesis of polyhydroxylated cispentacin analogues (Scheme 6).15... 

A sligth modification of this synthetic methodology allowed the development of a novel route to 4-amino-5-(hydroxymethyl)cyclopentane-l,2,3-triols, some of them display significant glycosidase inhibition properties. In addition, a similar approach starting from L-idose allowed the first polyhydroxylated dspentacine to be prepared.78... 

Im Falle der teilweise methylierten Derivate des L-Idosans sind einige Substanzen aus den betreffenden Athem der freien L-Idose, bzw. deren Derivaten, durch RingschluB bei Einwirkung von Sauren gewonnen worden lOAD. 

Auch beim Einengen der Losung der freien 6-Amino-6-desoxy-L-idose entsteht ein Idosan-Derivat mit Stickstoff im fiinfgliedrigen Ring 189-... 

Using the C-5 epimeriztion strategy used to convert D-glucose into L-idose, but starting with a D-galactoseptanose derivative (such as 47) delivered the L-altrose isomer 50 (Scheme 10). Treatment of 5-O-benzyl-1,2-O-isopropylidene-a-D-galactoseptanose... 

G. E. Driver and J. D. Stevens, Septanose carbohydrates. III. Oxidation-reduction products from 1,2-3,4-di-O-isopropylidene-a-D-glucoseptanose Preparation of L-idose derivatives, Aust. J. Chem., 43 (1990)2063-2081. 

L-idose or L-sorbose. More recently it has been prepared by the more convenient hydrogenation of these sugars. " ... 

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... 

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... 

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