As Alditols

A procedure has been reported473 for the direct determination, on a column of Polypak, of polyhydric compounds without conversion into derivatives. Separation of pentitols was not complete, but the method was found excellent for determining the amount of one alditol, as in the oxidation of L-arabinitol by Acetobacter suboxydans. This rapid method of monitoring the utilization of L-arabinitol permitted the reaction to be stopped as soon as all of the substrate had been consumed, before side reactions interfered. 

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Smith degradation of PI. A sample of FI (50 mg) was dissolved in 0.5 M NaOH (5 mL) and acetic acid added to pH 7, followed by NaI04 to a final concentration of 50 mM. At the conclusion of the oxidation (7 days) the product was reduced with NaBH4 and dialyzed. An aliquot was removed and the remainder immediately treated with NaI04 and then reduced with NaBH4. Samples of material subjected to one and two cycles of oxidation-reduction were hydrolyzed and reduced, and the products analyzed by GLC as alditol acetates. 

Englyst, H.N. and Cummings, J.H. (1984) Simplified method for the measurement of total non-starch polysaccharides by gas-liquid chromatography of constituent sugars as alditol acetates. Analyst 109, 937-942. 

Many bacterial polysaccharides have been analyzed as alditol acetates,15-16,18,53,420-431-447 and, for those that contain 3,6-dideoxy sugars,... 

All monosaccharides and their derivatives that possess aldehyde or ketone groups (that is, excepting derivatives such as alditols and aldonic acids) will have reducing properties. Moreover, those with the appropriate number of carbon atoms can form rings occurring in two forms (anomers) and in which the potential reducing carbon is called the anomeric carbon. 

Borchardet LG, Piper CV (1970) A gas chromatographic method for carbohydrates as alditol acetates Tappi 53 257-260... 

Fig. 1 Schematic for the permethylation linkage analysis, exemplified by a hypothetical trisaccharidc, Gal-(a-l,4)-Glc-(a-l,6)-Man. The acid-hydrolyzed partially methylated monosaccharides generated are analyzed by GC-MS, typically as alditol or aldononitrile derivatives...

The mixture of partially methylated sugars obtained on hydrolysis of fully methylated polysaccharides is routinely analyzed in the authors laboratory, as alditol acetates, by g.l.c.-m.s. For this reason, the mode of fragmentation of these derivatives has been extensively studied " by using the deuterium-labelling technique. The results of the studies are summarized next. 

All of the free hydroxyl groups are protected as acetals by reaction with methyl vinyl ether. The 0-acyl groups are then split off by treatment with alkali, and the resulting material is methylated (see Scheme 20). After hydrolysis of the methylated material, and analysis of the hy-drolyzate as alditol acetates by g.l.c.-m.s., it is possible to determine the positions and proportions of O-methyl groups and, hence, the substitution pattern of the 0-acyl groups. This procedure has been used to locate 0-acetyl groups in bacterial polysaccharides and wood polysaccharides. ... 

When the carbonyl group of a sugar is reduced to a hydroxyl group, the resulting compound is one of the polyhydroxy alcohols known as alditols. Two compounds of this kind, xylitol and sorbitol, derivatives of the sugars xylulose and sorbose, respectively, have commercial importance as sweeteners in sugarless chewing gum and candy. 

Methyl glycosides are of their greatest use when only a few methylated sugars are anticipated, as with polysaccharides of simple structure and, in particular, with oligosaccharides. They are useful where identification must be based on peak profile and retention times, but, when characterization is to be achieved by mass spectrometry, other derivatives, such as alditol acetates, are preferable (see Section XXI,2 p. 30). Glycosides have the advantage over alditols that they may be hydrolyzed to the free sugar for further characterization. 

Sephton was the first to apply trimethylsilylation to the analysis of the products obtained from a methylated xylan, and he demonstrated the excellent separation obtained in this way between 2- and 3-0-methyl-xylose. This discovery was significant, as these two compounds, for example, are not separable as alditol acetates, and thus this method has been utilized in the study of other xylans. ... 

Where the components of a mixture differ greatly in degree of methyl-ation, temperature programming may be used with advantage, and may be started at as low as 50°. Even with the use of this technique, there are some compounds not readily separated as alditol acetates, and for which other derivatives are preferable thus, 2- and 3-O-methylxyloses are not separable as the alditol acetates, but are resolved as the tri-methylsilyl derivatives. With mixtures of unknown composition, it is thus prudent to investigate the separation by trying different derivatives. 

Much of our knowledge on the fragmentation patterns of carbohydrate derivatives arises from studies on methylated monosaccharides, but in structural investigations, such compounds are seldom subjected to mass spectrometry. On the other hand, the molecular weight of a permethylated oligosaccharide is significantly less than that of the per(trimethylsilyl) derivative. For this reason, the mass spectra of disaccharides as -their permethylated alditols have been determined by Chizhov and coworkers, Karkkainen, and Krone and Beckey. Trisaccharides have also been studied by Karkkainen, either as permethylated glycosides or as alditols. ... 

As alditol pernaphthoates Reductive amination With ABEE With 2-aminopyridine With anthranilic acid With ANTS or AMAC Reducing sugars Reducing sugars 0.1 pmol 0.5 nmol 10 pmol lOOfmol 0.2 pmol ... 

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