Disaccharides permethylated

PA-1 was partially hydrolyzed with O.IM TFA (40°C, 24 h) and the three fractions (PA-l-I, PA-l-II and PA-l-III) were obtained by Bio-gel P-6. Especially, about 50% of TBA-positive material (PA-l-III) was eluted in the fraction of small oligosaccharide. Permethylated oligosaccharide-alditols from PA-l-III were analyzed by GC-EIMS, and three disaccharide-alditols (IP, 2P and 3P) were detected. EI-MS and component sugar analysis suggested that the major peak, IP was Rha-(l- 5)-Kdo-ol and the minor peaks, 2P and 3P were two epimers of Araf-( l->5)-Dha. 

A second method uses permethylation of the dephosphated (48% aqueous HF, 48 h, 4°C) and 2H-reduced fipid A. This approach allowed the assignment of amide-bound fatty acids linked to GlcN(I) and GlcN(II), as well as the identification of the backbone structure as a HexpN disaccharide (85). Mass-spectrometric analysis of the products was performed by using either a short g.l.c. column (0.3 X 5 cm) or by direct insertion-probe analysis (87). In the case of C. violaceum (85), the mass spectra obtained from the permethyl-ated HexpN disaccharide bearing attached TV-methylacyl residues revealed unequivocally that both amino groups carried 12 0(3-OH). 

In order to further study the anomeric configuration of glucosamine and the linkage site of glucosamine to glucosaminitol, the N-acetylated and reduced disaccharide was permethylated according to Hakomori (17) and subjected to gas-liquid chromatography. 

The carbohydrate sequence of the major tetrasaccharlde was determined by examining the nitrous acid deamination products (25) as permethylated disaccharides by chemical ionization mode of gas chromatography/mass spectrometry. The products were identified as hexosyl-2,5-anhydromannitol and hexosyl-myoinositol,indicating that the major tetrasaccharide had the sequence Galp(l->4)GlcNAcp(l->4)Glcp(l- -2)Inos (Figure 5). 

The mass-spectrometric behavior of permethylated disaccharides having (l- 2)-, (l->4)-, and (l->6)-linked hexose residues has been investigated by Kochetkov and coworkers. It was found that the fragmentation of both moieties of the disaccharide follows principles similar to those for permethylated glycosides. The nomenclature used by Chizhov and Kochetkov for the different fragmentation series of permethylated... 

The nature of the linkage between the residues in a permethylated disaccharide alditol can be determined by inspection of the fragments formed by cleavage of the alditol chain (cf. Section IV,3 p. 56). 

The mass spectra of trimethylsilylated disaccharide alditols are simplified because of the limited number of fragmentation routes for the alditol moiety. Molecular ions were not seen in the spectra, but, as for the per(trimethylsilyl)ated disaccharides, the (M — CHj) and (M — CH3 — MeaSiOH) can be used to determine molecular weights. The nature of the aldose and alditol residues can be established in the same way as for permethylated disaccharide alditols (see Section VI, 2 p. 89). The fragments formed by a-cleavage of the alditol chain indicate... 

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. ... 

Treating the hepta-iodo-) -CyD derivative with NaNs in DMF gave, in 96% yield, the hepta-azide, which was methylated using a large excess of Mel and NaH to afford the permethylated derivative quantitatively. Treatment with PhsP followed by aqueous NH3 furnished the hepta-amino-/ -CyD. The disaccharide[Pg.36]

Methylation Analysis. — Information on the m.s. of permethylated disaccharides has been recorded. Fragmentation mechanisms for the electron impact m.s. of twenty-two permethylated aldohexopyanosyl (1- x) aldoses, where x = 1-6, have been reported. Using high resolution measurements, data on metastable ions were obtained. 

Chemical ionization methods have been used with methyl ethers of methyl glycosides and have indicated that anomers with equatorial methoxy-groups decompose faster than those with axial groups. The same method applied to permethylated disaccharides allows better distinction between isomers than does the electron-impact method. A permethylated amino-sugar trisaccharide derivative has been studied as have permethylated dialdose anhydrides. ... 

Aspects of chemical methods used in the structural elucidation of polysaccharides and complex carbohydrates have been reviewed. In a critical examination of the use of g.l.c.-m.s. in the identification of TMS ethers of monosaccharides, a standardized method, which uses a medium resolution mass spectrometer and short chromatographic columns, has been proposed. TMS Ethers of monosaccharides have been characterized by g.l.c.-chemical ionization m.s. with ammonia as reagent gas. Molecular weights were determined, and fragment ions were produced in a quantity high enough to differentiate between stereoisomers (epimers and anomers). Disaccharides have been determined by permethylation followed by g.l.c. The method has been used in the detection of carbohydrate intolerance secondary to intestinal disaccharidase deficiency. 

The structures of disaccharides and disaccharide alditols were revealed by periodate oxidation, reduction and analysis of the products by e.i.- and FAB-m.s. as their peracetyl or permethyl derivatives. The compounds gave simple m.s. with intense and characteristic ions from which the glycosidic linkage positions and ring size could be determined. ... 

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