Hexopyranosides 3,4-anhydro

C13H2206 3,2 -Anhydro-[methyl 2,6-dideoxy-4-0-(3,6-dideoxy-a-D-riho-hexopyranosyl)-a-D-Zt/xo-hexopyranoside] (MADRFU)256... 

On their side, Yin and Linker [216] made use of a 2-C-branched hexopyranoside, the synthesis of which was achieved by addition of dimethyl malonate to tri-O-benzyl-D-glucal (TUPAC name 3,4,6-tri-0-benzyl-l,5-anhydro-2-deoxy-D-araZtino-hex-l-enitol, Scheme 45) [217], Thus, saponification of the 2-C-[bis(meth-oxycarbonyl)]methyl derivative 184 to the corresponding malonic acid 185 was followed by heating in refluxing toluene. This led to decarboxylation and lactoniza-tion giving 186. The method was optimized and applied to the synthesis of pentoses and disaccharides. 

Chart IV summarizes the reactions of these 2,3- and 3,4-anhydro-hexopyranosides. The half-chair conformations shown are those anticipated on the assumption that the alkyl substituent on C-5 governs the conformation assumed, as it usually does with the chair conforma-... 

Other Reactions NaOH — 3,6-anhydro-D-glucopyranoside72 3 (R OMe, R = H). Normal (Y = OMe)X = OMe.105 Abnormal Ethyl or benzyl 2,3-anhydro-4-deoxy-/3-DL-nbo-hexopyranosides gives 3-subs. Di.-xt/(o-hexopyrano-sides with NH3 or NHMe2.12es... 

Korte and coworkers15,5 and H. Newman86 did not separate their mixtures of stereoisomeric alkyl 2,3-anhydro-4,6-dideoxy-DL-hexopyrano-sides (248) in which the undesired a-lyxo stereoisomer was certainly the preponderant component. In consequence, racemic alkyl desosa-minide was obtained only as a minor product in admixture with alkyl 3,4,6-trideoxy-3-(dimethylamino)-DL-flr / ino-hexopyranoside (250),... 

J. Yoshimura, N. Kawauchi, T. Yasumori, K.-l. Sato, and H. Hashimoto, Synthesis of 2,3-anhydro- and 3,4-anhydro-hexopyranosides having a methylbranch on the oxirane ring, and their reactions with some lithium methylcuprate reagents, Carbohydr. Res. 133 255 (1984). 

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... 

All stereocenters in 1,6-anhydrohexopyranoses are of inverted orientation compared to those in the parent 4Ci(d) or 1C4(l) conformations of the corresponding hexopyranoses for example, see 21, 23, and l,6-anhydro-/J-D-glucopyranose (22). In chemical properties, these compounds resemble to a certain degree the methyl /f-D-hexopyranosides. They are relatively stable in alkaline media, but are readily hydrolyzed by acids. In aqueous acid solution, an equilibrium is established between the 1,6-anhydrohexo-pyranose and the corresponding aldohexose, whose composition correlates with expectations from conformational analysis and calculations from thermodynamic data.121 Extreme values, 0.2 and 86%, are observed respectively with 1,6-anhydro-/f-D-glucopyranose (22) and l,6-anhydro-/f-D-idopyranose (the latter has all hydroxyl groups in equatorial disposition). 

All cofigurational isomers of 2,3- and 3,4-anhydrohexopyranoses have been described. Generally, they adopt more or less flexible half-chair conformations (H) dependent on the absence or presence of an additional fused ring. Examples of the latter compounds are methyl 2,3-anhydro-4,6-O-benzylidene-a- and /1-hexopyranosides of the alio 70,272,273 manno 71,273 275 gui0 216,211 an(j 276 c0nfigurati0nS. 

P. L. Barili, G. Berti, G. Catelani, F. Colonna, and E. Mastrorilli, Alkaline and enzymatic hydrolysis of isobutyl 3,4-anhydro-2,6-dideoxy-DL-hexopyranosides. Preparation of enantiomeric boivinopyranosides through a highly efficient kinetic resolution, J. Org. Chem., 52 (1987) 2886-2892. 

P. Koll and F. S. Tayman, 2,5-Dioxabicyclo[2.2.2]octan-Derivate Methyl-2,6-anhydro-D-hexopyranoside mit talo- und aftro-Konfiguration, Chem. Ber., 112 (1979) 2296-2304. 

D. Horton and J. S. Jewell, l,6-Anhydros-2,3-0-isopropylidene-/8-D-/yxo-hexopyranosid-4-ulose. Studies on oxidation of carbohydrate derivatives, Carbohydr. Res., 2 (1966) 251-260. 

A 3 M solution of t-butylhydroperoxide in toluene (0.042 ml, 0.12 mmol), titanium tetraisopropoxide (0.008 ml, 0.02 mmol) and ethyl diisopropylamine (0.014 ml, 0.08 mmol) were added to a stirred solution of 40 mg (0.074 mmol) of phenyl 4,6-di-0-benzoyl-2,3-dideoxy-3,3-difluoro-l-seleno-a-D-erythro-hexopyranoside in 4 ml of anhydrous dichloromethane at room temperature. The reaction was complete within 6 h, and the solvent was then evaporated to dryness and the residue was quickly purified by preparative TLC to give 20 mg (72%) of l,5-anhydro-4,6-di-0-benzoyl-2,3-dideoxy-3,3-difluoro-D-erythro-hex-l-enitol. 

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