Methyl glucopyranosides

Making a methyl glucopyranoside is relatively straightforward in that we can use the alcohol methanol as solvent, and, since it is thus present in large excess, this helps to disturb the equilibrium. The process is much less attractive for a... 

Look at the structure of methyl -glucopyranoside (Figure 4 29) and satisfy yourself that it has seven non-equivalent carbon atoms. You might also try to assign the two extreme signals. 

Similar results have been obtained with the tetra-O-trimethylsilyl derivatives of the anomers of methyl glucopyranoside, methyl galacto-pyranoside, and methyl mannopyranoside. The 17 ev mass spectrum of the tetra-O-trimethylsilylated form of the anomers of methyl glucoside are shown in Figure 7. Again the traces are similar, but intensity differences are discernible. The ratio (377/361 )i7ev has proved most useful. 

Compounds such as methyl glucopyranoside differ in reactivity from the parent monosaccharide. For example, unmodified glucose reacts with oxidizing agents such as cupric ion (Cu ) because the open-chain form has a tree aldehyde group that is readily oxidized. 

Oxv jen source. Does the oxygen atom attached to (M in methyl [ )-glucopyranoside come from glucose or methaiujl ... 

The acid-catalyzed hydrolysis of a- and (1-methyl glucopyranosides has been studied with multiple KIEs.22,25 Scheme 6 presents a composite representation of the isotop-ically substituted positions used in the studies. Table 1 presents selected KIE results. 

Ozonization of a- and -methyl glucopyranosides has also been examined. The latter are converted into the corresponding 5-acetoxyaldonic acid methyl esters, whereas the former are recovered unchanged. The polyacetyl derivatives are used to protect hydroxyl functions. The difference in reactivity of a- and jj-anomers can be used to purify a-anomers. 

Miscellaneous. Methyl glucopyranosides and glycopyranosyl chlorides undergo allylation with allylsilanes under TMSOTf catalysis to give predominantly a-allylated carbohydrate analogs (eq 24).33... 

Marshall RD (1963) Rates of acid hydrolysis of 2-substituted methyl glucopyranosides. Nature 199 998-999... 

On methylation followed by methanolysis, Rg yielded only methyl 2,3,4,6-tetra-o-methyl-glucopyranoside. As the coupling constants of both anomeric proton signals of (46) indicated P-configuration, structure of Rgj was established as 6,20-di-o-P-D-glucopyranosyl-20(5)-protopanaxatriol... 

Effects of neighbouring-group participation in the acid-catalysed hydrolysis of 2-0-substituted methyl glucopyranosides have been studied kinetically arming ... 

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