Oxidation Products from Monosaccharide Derivatives and Related Compounds

Oxidation Products from Monosaccharide Derivatives and Related Compounds 

To jdeld a dialdehyde on periodate oxidation, a monosaccharide derivative must be held in a ring form by suitable substituents. The oxidation products can be divided into two classes those which generally do not contain hydroxyl groups elsewhere in the molecule, and form hemialdals, for example (3), and those which can form internal hemiacetals with a hydroxyl group elsewhere in the molecule, for example (4) the latter class 

Oxidation destroys the asymmetry of the sugar molecule and, consequently, the same oxidation products may be obtained from the same derivative of several different sugars. For example, oxidation of any methyl a-D-pentopyranoside would yield (3) as the product. 

The dialdehyde monohydrate from methyl a-u-rhamnopyranoside has been shown to possess the hemialdal structure (8) since it forms a di-p-nitrobenzoate, and methylation with methyl iodide and silver oxide introduces two more methoxyl groups. Also, the dialdehyde monohydrate, and its enantiomorph, show no infrared carbonyl absorption, but show hy- 

The formation of the hemialdal (11) has been presumed to occur by hydration of one aldehyde group followed by ring closure, as follows. Such a system allows for the possible formation of four isomers, although 

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IV. Oxidation Products from Monosaccharide Derivatives and Related Compounds. 108... 

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