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Preparative Use of Uronates Having an Endocyclic, Enolacetal Linkage

Preparative Use of Uronates Having an Endocyclic, Enolacetal Linkage [Pg.285]

Pyranuronates and furanuronates having an enolacetal linkage are readily prepared, for example, by the alkali-catalyzed, sulfonate or phosphate j3-elimination reaction. Such unsaturated uronates have proved to be valuable starting-materials in the preparation of divers rare sugars and sugar conjugates. Nevertheless, only a few publications in this interesting field have thus far appeared. [Pg.285]

5-Unsaturated 4-deoxyhexopyranuronates, especially their 0-benzyl-ated derivatives, such as 195, proved to be readily converted into the corresponding 5-(hydroxymethyl) derivatives (196), by complex metal hydrides, such as sodium borohydride or lithium aluminum hy-dride.  [Pg.286]

The anomeric effect of the a and p anomers of alkyl 4,5-unsaturated 4-deoxyhexopyranuronates in the hydrogenation was proved exactly by Schmidt and Neukom by using catalytic hydrogenation. It was found that the two anomers of 4,5-unsaturated 4-deoxyhexopyranuronates exist in two different H and H ) conformations and that this influences the stereochemistry of addition of hydrogen to the enolacetal double bond. [Pg.287]

By catalytic hydrogenation with hydrogen in the presence of 10% palladium-on-charcoal in dry methanol at 22-24°, methyl (methyl 4-deoxy-j8-L-threo-hex-4-enopyranosid)uronate (200) gives a mixture of methyl (methyl 4-deoxy-a-D-xy/o-hexopyranosid) uronate (201) and methyl (methyl 4-deoxy-j8-L-arabino-hexopyranosid)uronate (202) in the ratio 7 43. [Pg.287]




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2- uronate

Endocyclic

Preparative use

Uronates

Urones

Uronic

Useful Preparations

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