Hexoside methyl 4-deoxy

Anhydro-3,4-O-isopropylidene-2-O-toayl-/3-D-altrose Methyl 2,0-dideoxy-3-O-methyl-4-O-tosyl-a-D-xylo-hexoside Methyl 2,6-dideoxy-3-0-methyl-4-0-tosyl-/3-D- ct/lo-hexoside 0-Deoxy-2,3-O-isopropylidene-l-O-tosyl-L-sorhose 2,4 3,5-Di-0-methylene-l-0-tosyl-D-epirhamnitol... 

Hexoside, methyl 4,6-0-benzylidene-2,3-dideoxy-P-D-erythro-, 276 Hexulofuranose,6-amino-6-deoxy-L-xi/lo-, 142... 

Methyl 2-deoxy-39496-tri-0-p-nitrobenzoyl-p-T>- yxo-hexoside. A solution of 370 mg. of 2-deoxy-3,4,6-tri-0-p-nitrobenzoyl- -D-Zyxo-hexosyl bromide (5) in 15 ml. of dry dichloromethane is added to a stirred suspension of 500 mg. of silver carbonate in 100 ml. of absolute methanol. The mixture is stirred for 20 hours and filtered the silver salts are washed several times with warm dichloromethane. The combined filtrate and washings are evaporated to dryness under diminished pressure, and the residue is recrystallized five times from ether-dichloromethane, giving 61% of pure product, having m.p. 173°-174°C. and [ ]D + 36° in chloroform. 

Methyl 2-deoxy-P-v- yxo-hexopyranoside. A suspension of 170 mg. of the nitrobenzoylated hexoside (obtained in the preceding preparation) in 50 ml. of 0.01M methanolic sodium methoxide is stirred for 4 hours at room temperature. The solvent is removed at 40°C. under diminished pressure, and the residue is suspended in 15 ml. of water. The suspension... 

Rearrangement of methyl 4,6-0-benzylidene-3-deoxy-3-phenylazo-aldohexopyranosides with alkali provides a new route to hexosid-3-uloses (18). 

Methyl-3,6-di-0-benzoyl-2-deoxy-a-D- Methyl-3,6-di-0=-benzoyl-2-deoxy-a-D-t/ reo-hexosid-4-ulose S [317]... 

An interesting application of the reaction with sulfuryl chloride consisted in the synthesis of a fully chlorinated hexoside.27 Treatment of methyl 2-chloro-2-deoxy-/3-D-galactopyranoside with sulfuryl chloride and pyridine in chloroform, followed by heating of the product with an excess of pyridinium chloride, afforded a tetrachloride, presumably methyl 2,3,4,6-tetrachloro-2,3,4,6-tetradeoxy-/3-D-allopy-ranoside. 

On treatment with sodium ethoxide in ethanol, methyl 2,4,6-tri-O-methyl-a- (72) and -/3-D-ribo-hexosid-3-ulose yielded l-deoxy-2-methoxy-4,6-di-0-methyl-D-hex-l-en-3-ulose (73) and several isomeric ethyl 2,3,6-tri-0-methylhexosid-3-uloses (74) (see Scheme 10).133 On alkaline degradation of methyl 2,3-di-0-ethyl-6-0-pro-pyl-a-D-xy/o-hexosid-4-ulose (75) with sodium 1-butoxide in 1-butanol, one mole of ethanol was released per mole of 75, indicating that the substituent at C-2 was preferentially eliminated. On mild, acid hydrolysis of the product, methanol, ethanol, and some 1-propanol were formed, consistent with fission at C-l, C-3, and, to some extent, C-6 (see Scheme 10).134... 

Vis and Karrer114 have found that treatment of methyl 4,6-O-benzyl-idene-2,3-O-p-tolylsulfonyl-a-D-glucoside (13) with lithium aluminum hydride provides methyl 4,6-0-benzylidene-3-deoxy-a-D-n 6o-hexoside (IS) in good yield. Since hydrogenolysis is possible at both C-2 and C-3 of the two possible 2,3-anhydro derivatives, only the alio isomer (14) could give the 3-deoxy derivative by further reaction with a reagent. Indeed, none of the alternative 2-deoxy derivative was found. This transformation is, un-... 

The method employing triphenyl phosphite methiodide, as adapted to carbohydrates,130 has been used for the synthesis of protected 4-deoxy sugars. From methyl 2,3-di-0-methyl-6-0-p-tolylsulfonyl-a-D-glucoside and the corresponding D-galactoside, epimeric 4-iodo derivatives were obtained these were both reduced to methyl 4-deoxy-2,3-di-0-methyl-b-0-p-tolyl-sulfonyl-a-D-zj/Zo-hexoside. 

The first of these methods involves the reaction of triphenyl phosphite methiodide with methyl 3-0-methyl-2-0-p-tolylsulfonyl-a-D-glucopyrano-side, hydrogenation of the resulting 4,6-diiodo derivative, and hydrolysis,186 as adapted to monosaccharides by Kochetkov and coworkers.1,0 In another approach,281 ethyl 2,3-anhydro-4,6-dideoxy-D-nbo-hexopyranoside, obtained from desosamine, was treated with sodium methoxide, to give a mixture of 2- and 3-methyl ethers. After fractionation and separation of side products,288 the 3-methyl ether was hydrolyzed, to give crystalline chalcose. McNally and Overend800 have described another synthesis, starting from methyl 4-deoxy-D-xj/Zo-hexoside.107... 

Deoxy-D-arafnno-hexose (55) was treated in methanol with hydrogen chloride according to a procedure79 which was purported to yield almost exclusively a mixture of the anomers of methyl 2-deoxy-D-arabino-hexofur anoside. It has now been shown78 that the latter consists, in fact, of an anomerically pure methyl 2-deoxy-D-arabino-hexofuranoside (77), plus substantial proportions of an approximately 1 1 mixture of methyl 2-deoxy-a- and jS-D-orabmo-hexopyranosides (78) and (79), and unreacted 2-deoxy-D-arabino-hexose (55). p-Nitrobenzoylation of the sirupy, quadripartite mixture led to a mixture of p-nitrobenzoic esters from which, by fractional recrystallization, there was obtained in pure form a methyl 2-deoxy-3,5,6-tri-O-p-nitrobenzoyl-D-arabino-hexoside (80). Attempts to replace, directly, the severely hindered methoxyl group at C-l of (80) by halide failed. 

Chlorosulphate as a Leaving Group The Synthesis of a Methyl Tetrachloro-tetra-deoxy-hexoside, A. G. Cottrell, E. Buncel, and J. K. N. Jones, Chem. Ind. (London), (1966) 552. 

S-Deoxy-D-xyJo-hexose — methyl 3-deoxy-D-xj/lo-hexoside 2 Nal f tone 3,6-dideoxy-6-iodo-D-a j/lo-hexo8ide —eduction jjjethyl 3,6-dideoxy-D-a /o-hexoside... 

Reduction of methyl 4,6-0-benzylidene-2,3-di-0-p-tolylsulfbnyl-a-D-glucopyranoside with lithium aluminum hydride in tetiahydrofuran affords methyl 4,6-0-benzylidene-3-deoxy-a-D-fifco-hexopyranoside (in 66% yield) by a mechanism analogous to that proposed by Overend and coworkers for the formation of 5-deoxy-l,2-0-isopropyli-dene-a-D-x /lo-hexofuranose. With the corresponding /3-d anomer, hydride reduction in tetrahydrofuran proceeds less readily, giving methyl 4,6-0-benzylidene-3-deoxy-/8-D-rtho-hexopyranoside in 38% yield. This compound was also obtained (in 22% yield) when hydride reduction was performed in p-dioxane, together with a second crystalline compound, identified as methyl 4,6-0-benzylidene-2,3-dideoxy-/3-D-er /thro-hexoside formed by direct displacement at C-2 and C-3 with hydride. 

The resistance of large equatorial substituents at C5 to the postulated conformational transformations of the above cyclic intermediates readily accounts for the decreasing rates of hydrolysis of 6-deoxy hexosides, hexo-sides, and heptosides, as compared with those of pentosides " (see Tables IV, V, and VII). Nevertheless, there is a strong possibility that this decrease in the rates of reaction may be due to the respective polar effects of the —CH3, —CH2OH, and —CHOH— CH20H substituents, as noted for methyl 6-deoxy-a- and /S-L-mannopyranoside. 

Zorbach and coworkers180 obtained methyl 2-deoxy-a- and /J-D-ribo-hexosides (a /3 = 3 17) by treatment of 2-deoxy-3,5,6-tri-0-(p-nitro-benzoyl)-a-D-nbo-hexosyl bromide with methanol in the presence of silver carbonate. 

These pyranoid compounds offer a means of obtaining 1-deoxy-ketoses (seep. 259), and continue to provide a source ofaldos-5-uloses the sugar component of hygromycin A has thus been prepared by hydrolyzing methyl 6-deoxy-a-D-arafcino-hex-5-enopyranoside.149 In related fashion, methyl 6-deoxy-2,3-0-isopropylidene-a-D-Zyxo-hex-5-enopyranoside (81) was isomerized150 in the presence of an acid to methyl 6-deoxy-2,3-0-isopropylidene-a-D-Zyxo-hexosid-5-ulose (82). 

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