Arabinopyranoside, methyl 3 anomer

Many other glycosides have been subjected to selective chlorination with sulfuryl chloride. Methyl /3-L-arabinopyranoside afforded methyl 4-chloro-4-deoxy-a-D-xylopyranoside 2,3-di(chlorosulfate) in 29% yield, whereas the a-L anomer gave357 methyl 3,4-dichloro-3,4-dideoxy-/3-i)-ribopyranoside 2-(chlorosulfate) (30%). Methyl /3-d-ribopyranoside was converted into methyl 3,4-dichloro-3,4-dideoxy-a-L-arabinopyranoside through the action of pyridine hydrochloride on its 2,3,4-tri(chlorosulfate).358 Methyl a-D-lyxopyranoside gave only the 2,3,4-tri(chlorosulfate),353 as would be expected from the disposition of its hydroxyl groups, similar to that in the rhamno- and manno-pyranosides. Methyl a-D-altropyranoside was transformed into the 6-chloro-6-deoxy 2,3,4-tri(chlorosulfate) derivative in 80% yield.353... 

In the 3,4-anhydro-arabinose series, only the hydrolysis of the anomers of methyl 2-0-acetyl-3,4-anhydro-D-arabinopyranoside with aqueous acetic acid appears to have been studied 68 both compounds undergo substitution at C-3, with participation of the acetoxyl group, leading to the corresponding D-lyxose derivatives. 

In Ref. 1 (pp. 1114-1115) the effect of the axial or equatorial orientation of the aglycon in the rate of oxidation of a number of /f-D-glycopyranosides is described. When the aglycon adopts an equatorial orientation [a / anomer in the 4Ci(d) conformation] the oxidation takes place at a higher rate (two to ten times) than for the a anomer. In the case of methyl L-arabinopyranosides, the a-L anomer, which, in the (l) conformation has an equatorially attached group at C-l, is oxidized more rapidly. 

By this method both anomers of methyl DL-arabinopyranoside and -DL-ri-bopyranosidc were obtained.In a similar manner, normal and 6-deoxy methyl DL-hexopyranosides of the alio, altro, galacio, and talo configuration, and esters of DL-hexuronic acids of altro, galacto, and talo configuration were prepared. 

The oxidation of glycosides to glycosid-4-uloses using Acetobacter suboxy-dans reported last year (see Vol. 11, p. 129) has been further investigated the a-anomers of methyl d- and L-arabinopyranoside and D-lyxopyranoside were slowly oxidized at C-4 with moderate efficiency, whilst the j8-anomers of methyl L-arabino- and D-ribopyranoside were oxidized at C-2 the specificity of the enzyme system towards methyl glycopyranosides was discussed, and n.m.r. data on the glycosidulose O-methyl oximes recorded. ... 

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