Hexofuranose 5.6- anhydro

The potentialities of this method are such that, with the proper choice of hexofuranose derivative, access can be gained to 2,5-anhydroaldoses in which the side chains have the cis orientation, as would be required for further elaboration into C-nucleosides. Matsui and coworkers62 reported the synthesis of modified C-nucleosides by acidic treatment of 3-0-benzyl-l,2-0-isopropylidene-5,6-di-0-(methylsulfonyl)-/3-L-talofuranose (60), to give 2,5-anhydro-3-0-benzyl-6-0-(methylsulfonyl)-aidehydo-D-allose dimethyl acetal (61). 

The addition of iodine trifluoroacetate (produced by reaction of iodine with silver trifluoroacetate) to unsaturated carbohydrates has been investigated.134 Treatment of 5,6-dideoxy-l,2-0-isopropylidene-a-D-xylo-hex-5-enofuranose (89) with silver trifluoroacetate and iodine in acetonitrile gave 3,6-anhydro-5-deoxy-5-iodo-l,2-0-iso-propylidene-a-D-gluco(and /3-L-ido)furanose (91) and 5-deoxy-5-iodo-l,2-0-isopropylidene-6-0-(trifluoroacetyl)-o -D-gluco(and/or /3-L-ido)-furanose (92), with the former preponderating. Component 91 was converted into 3,6-anhydro-5-deoxy-l,2-0-isopropylidene-a-D-xj/io-hexofuranose (94) by hydrogenation over Raney nickel (see also, Section III,3 p. 299), and component 92 was converted into 5-deoxy-l,2-0-isopropylidene-a-D-xy/o-hexofuranose (95) by treat-... 

Anhydro-3-deoxy-l,2-0-isopropylidene-a-D-x //o-hexofuranose— 3-deoxy-D-x /io-hexose 6-phosphate.207... 

Deoxy-6-thio-D-a yfo-hexose forms a 1,6-anhydro compound analogous to 270. S-Acetyl-5-deoxy-l,2-0-isopropylidene-6-thio-a-D-xyZo-hexofuranose is obtained either by nucleophilic displacement on the corresponding 6-p-tolylsulfonyloxy compound with potassium thioacetate or by the photochemical addition of thioacetic acid to... 

Other studies of selective sulfonylation at a primary hydroxyl group of sugars were made with 5-deoxy-l,2-0-isopropylidene-a-D-xy/o-hexofuranose at —12° to give the 6-p-toluenesulfonate and 6-methanesulfonate. On wanning the reaction mixture to 25°, these derivatives were converted into 3,6-anhydro-5-deoxy-l,2-0-isopropyl-idene-a-D-xyio-hexofuranose. The formation of 2,5-anhydrides on p-toluenesulfonylation of dialkyl dithioacetals of pentoses probably proceeds similarly, through the 5-p-toluenesulfonates. 

In general, on reaction with lithium aluminum hydride, secondary sulfonic esters are desulfonylated, with formation of the corresponding secondary alcohol. An exception is provided in an observation by Reist and coworkers, who treated 6-0-benzoyl-l,2-0-isopropyli-dene-5-O-p-tolylsulfonyl-a-D-glucofuranose, with lithium aluminum hydride in ether and obtained a product thought to be 6-deoxy-l,2-0-isopropylidene-y3-L-idofuranose, derived from an intermediate 5,6-anhydro-L-ido derivative later, Ryan and coworkers showed, from its nuclear magnetic resonance spectrum, that the product was 5-deoxy-l,2-0-isopropylidene-a-D- t/Zo-hexofuranose. The problem has been re-examined by Overend and coworkers the repetition experiment under the conditions of Reist and coworkers afforded 5-deoxy-... 

Hexofuranose, 3,6-anhydro-5-deoxy-l,2-O-isopropylidene-a-D-xylo-, 241 —, 5 - deoxy -1,2 - O - isopropylidene - a - D -xylo-, 275... 

Kashino, S., Inokawa, S., Haisa, M., Yasuoka, N., and Kakudo, M., The structure and absolute configuration of (5R)-5,6-anhydro-3-0-benzyl-l,2-0-isopropylidene-5-C-(dimethoxyphosphinoyl)-a-D-AyZo-hexofuranose, Acta Crystallogr, Sect. B, 37, 1572, 1981. 

As far as the nitrogen analogs are concerned, l,6-anhydro-(6-aceta-mido-2,3-di-0-acetyl-5,6-dideoxy-/3-D-xf/lo-hexofuranose) (260) was isolated after acetylation of the equilibrium mixture prepared from the corresponding 6-amino-5,6-dideoxyhexofuranose the original mixture also contained the parent sugar and traces of two additional azepine compounds.784... 

Hexopyranosldes (D-gluco, D-manno, D-galacto, 2-acetamido-2-deoxy-D-gluco. and a,a-trehalose) were converted into their 3j6-anhydrldes by treatment of their previously reported stable crystalline 6-oxytris(dimethylamino)phosphonium hexafluorophosphate salts with alkali (MeOH-MeONa).The four possible 3,6-anhydro-hexofuranoses, together with their triacetates, methyl glycosides, and glycoside diacetates, have been synthesized, mainly from the known 3 6-anhydrohexopyranoses, and equilibria between the anomerlc... 

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