Alditols partially methylated, mass spectrometry

The proposed structure is in full agreement with the results obtained by mass spectrometry, immunodiffusion and analysis of partially methylated alditol acetates (4). 

Figure 1. Methylation linkage analysis of PSL-I by GC/MS total ion chromatogram of partially methylated alditol and myoinositol acetates (PMAA) from PSL-I carboxyl-reduced trisaccharide by gas chromatography /mass spectrometry in...

Plasma-desorption mass spectrometry is another technique that has been applied successfully to the detection of readily removable fatty acyl substituents in intact glycolipids and their acylated derivatives. The specific location of the fatty acyl substituents in the ring of the glycosyl residues, as in LOS antigens, is determined by methylation under nonbasic conditions (see Section II.lb), followed successively by O-deacylation, ethylation of the exposed hydroxyl groups, and GC-MS analysis of partially alkylated alditol acetates21 ethyl groups denote the sites of previous O-acylation. 

Carpita NC, Shea EM (1989) Linkage structure of carbohydrates by gas chromotography-mass spectrometry (GC-MS) of partially methylated alditol acetates. In Biermann CJ, McGinnis GD (eds) Analysis of carbohydrates by GLC and MS. CRC Press, Boca Raton, FL, p 157... 

Methylation is the most widely used method to determine the position of the glycosyl linkages.Permethylation of glycolipids can be done according to the methods of Hakomori (32) and Ciucanu and Kerek (33). The permethylated derivatives are hydrolyzed and the products converted into partially methylated alditol acetates and identified by gas chromatography-mass spectrometry ( CG-MS) (34). 

Funakoshi, I., Yamashina, I. (1980). Quantitative determination of partially methylated alditol acetate of amino sugar by gas chromatography-mass spectrometry. Analytical Biochemistry, 107, 265 270. 

The use of alditol acetates for the separation of mixtures of partially methylated sugars not only simplifies the g.l.c. but also the mass spectra, because such compounds contain carbon to carbon bonds of only three types those between (a) carbon atoms that each carries a methoxyl group, or (b) each bears an acetoxyl group, or (c) adjacent carbon atoms having one substituent of each type. Mass spectrometry of partially methylated alditol acetates thus gives rise to relatively few primary fragments that are characteristic of the pattern of substitution. This technique was introduced to carbohydrate chemistry by Lindberg and his associates, and has been employed extensively by them in subsequent structural studies, some of which are discussed next others are listed in Table XXXI (see p. 103). 

The use of mass spectrometry in the structural analysis of carbohydrates, first reported in 1958 (114), was developed in detail by Kochetkov and Chizhov (115). They showed that, under electron impact, the acetylated and methyl ether derivatives of monosaccharides provided a wealth of structural information through analysis of typical fragmentation pathways of the initial molecular ion. This has proved of enormous utility in the structural elucidation of polysaccharides and complex oligosaccharides sequential permethylation, hydrolysis, reduction to the alditol, and acetylation, affords mixtures of peracetylated, partially methylated alditol acetates that can be separated and analyzed by use of a gas chromatograph coupled directly to a mass spectrometer (25). The mass spectra of stereoisomers are normally identical, while the gas chromatographic retention times readily permit differentiation of stereoisomers. 

Thevis, M., Opfermann, G., and Schanzer, W. (2000) Mass spectrometry of partially methylated alditol acetates derived from hydroxyethyl starch. 

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