Hexopyranoses, 1,2-anhydro

Qualitative relaxation-studies have also been reported for an extensive series of derivatives of inositols, pentopyranoses, l,6-anhydro-/3-D-hexopyranoses, furanoses, and septanoses. In all instances, the experimentally determined Ri(ns) values reflect the anticipated geometry. For the furanose derivatives especially, they provide a better means for distinguishing between epimeric pairs than the relatively ambiguous interpretation of coupling-constant data. 

Anhydro derivatives of 2,4-dideoxy-2-fluoro-/3-D-xyZo-hexopy-ranose and 2,3-dideoxy-2-fluoro-/3-D-rtfco-hexopyranose, and the corresponding, reducing sugars, have been synthesized from 1,6-anhydro-... 

Aus 1,6-Anhydro-4-desoxy-2,3-di-0-p-toluolsulfonyl- p-D- vy/o-hexo-pyranose entsteht durch Einwirkung von CHaONa l,6-2,3-Dianhydro-4-desoxy-p-D-n o-hexopyranose, die weiter mit waBrigem Kaliumhydroxid selektiv zu l,6-Anhydro-4-desoxy-p-D-xy/o-hexopyranose geoffnet wird 33,34) ... 

Desoxy-1,6-anhydro-p-D-arafttno-hexopyranose Syrup —33,1° (CaHsOH) 65) ... 

For the conversion of l,6 2,3-dianhydro-4-deoxy- and l,6 3,4-dian-hydro-2-deoxy-/3-DL-(i/ ro-hexopyranoses (261 and 262) lithium diethylamide was successfully employed.151 However, attempts at isomerization of methyl 2,3-anhydro-4-deoxy- or -4,6-dideoxy-DL-hex-opyranosides (263 R1 = CH2OH, CH3, R2 = Me) with butyllithium failed, because of predominance of secondary reactions (for example, opening of the oxirane ring with BuLi).14(i The yields of desired products were negligible or nil. 

M. Sharma and R. K. Brown, The mechanism of the reaction of methyllithium with 2,3-anhydro-4,6 () ben/.ylidcnc-a-n-allopyranoside to form 4.6-(l-bcn/ylidcnc 1,2-didehydro-1,2-dideoxy-2-methyl-D-nbo-hexopyranose, Can. J. Chem. 46 151 (1968). 

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). 

The following 1,6-anhydro-/f-D-hexopyranoses have been described122 alio,123 125 altro 126,121 gluco,128 manno,110,129 131 gulo,132 ido,133 galacto,134 and talo.135 Only a few of these are known in the L configuration, for example ido136a,b or as racemates.137... 

Intramolecular oxirane-ring opening at C-4 substituted anhydride 148, where Nu = -0 (CH2CH2) OH or -O (CH2)raNH2, affords a new heterocyclic ring fused to 1,6-anhydro-jS-D-hexopyranose.443... 

In the case of 1,6 2,3- (136) and l,6 3,4-dianhydro-/I-D-talopyranoses, the diaxial opening of the oxirane ring prevails, but a trend to diequatorial opening496 498 is apparent with l,6 2,3-dianhydro-4-deoxy- and 1,6 3,4-dianhydro-2-deoxy-/l-D-/yxo-hexopyranoses.169,432,493 Using 1,6 2,3- and l,6 3,4-dianhydrohexopyranoses as starting compounds allowed the preparation of a complete series of 12 isomeric 1,6-anhydro-monodeoxy-/Fn-hexopyranoses and 6 corresponding 1,6-anhydro-dideoxyhexoses,499 mainly by catalytic or complex hydride reductions.462,500... 

J. PeckaandM. Cerny, Syntheses with anhydro sugars. 15. Syntheses of l,6-anhydro-2,3,4-trideoxy-jS-D-glycero-hexopyranose and its unsaturated derivatives as model substances for studying the optical rotation of sugars, Collect. Czech. Chem. Commun., 38 (1973) 132-142. 

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