Of trisaccharides

Xanthan gum is a long-chain polysaccharide composed of the sugars glucose, mannose, and glucuronic acid. The backbone is similar to cellulose, with added side chains of trisaccharides (three sugars in a chain). 

If derivatives are to be named on the basis of the trivial name, the component cited last in the systematic name receives locants with no primes, the preceding component singly-primed locants, etc. However, naming of trisaccharide and higher oligosaccharide derivatives systematically is preferred, to avoid ambiguity. 

K. Matsuoka, M. Terabatake, Y. Esumi, D. Terunuma, and H. Kuzuhara, Synthetic assembly of trisaccharide moieties of globotriaosyl ceramide using carbosilane dendrimers as cores. A new type of functional glyco-material, Tetrahedron Lett., 40 (1999) 7839-7842. 

The activity of tomato endo-D-galacturonanase follows action pattern B (see Scheme 1), which is characterized by an alternative cleavage of tetra(D-galactosiduronic acid) and by a relatively rapid degradation of trisaccharide.128 In the tetrasaccharide, bond 1 is split faster than bond 2. Bond 3 is not broken by the enzyme. Both the reduced and oxidized tetra(D-galactosiduronic acid) derivatives are hydrolyzed by this enzyme at bond 2. 

Figure 2.8 Orthogonal synthesis leading to combinatorial library of trisaccharides.

Studying the influence of the activator and using the MPEG-DOX-OH support (Scheme 4.18),12 the same group reported the synthesis of trisaccharide 79 using donors 76 and 78 both glycosylations were performed by action of 3 equiv of donor, in the presence of 0.1 equiv of dibutylboron triflate (DBBOTf) as activator and 4-A molecular sieves at -45°C for 30 min. 

Fucosyl phosphate 36 also very efficiently glycosylated the C4 position of acceptor 32. The orthogonality of the activating conditions of thioglycosides and glycosyl phosphate donors was exploited in the synthesis of trisaccharide glycal 41 (Scheme 6.7A).32 Furthermore, the different reactivity of a- and p-glycosyl phosphates was... 

In 1994, Takahashi and coworkers10 11 described another one-pot synthesis of trisaccharides using sequential additions of various glycoside donors and their corresponding activators.10 The first transformation relies on the activation of a... 

For the galactosylation reactions, 2,3,4,6-tetra-O-benzylgalactopyranosyl trichloroacetimidate 2 and dibenzylphosphite 10 were used as donors (Table 12.1). Under these conditions, the (5-(l—>3)- and (5-(l—>4)-linked disaccharides 16 and 17 were formed in only minor amounts (entries 1 and 2). To increase the proportion of the (5-anomers, the peracetylated galactopyranosyl trichloroacetimidate 11 was used as the donor. Reactions were poor in DMF, but in dioxane, a clean mixture of products was obtained. Two equivalents of donor were required to give a conversion of 20-30% of 1 to disaccharides 13-18. Peaks eluting when the column was washed with more polar solvent mixtures suggested that only traces of trisaccharides were formed, but the identity of these peaks was not investigated. 

Figure 12.11 XH NMR spectra of trisaccharide libraries obtained by random fucosylation of disaccharides 16-18.

The monosaccharide D-( + )-glucose, an aldohexose, is formed by plants in photosynthesis and is converted to the polysaccharides cellulose and starch. Simple saccharides are called sugars. Polysaccharides are hydrolyzable to monosaccharides e.g., a mol of trisaccharide gives 3 mol of monosaccharides. 

The analytical data do not exclude the possible presence of some tetra-saccharide residues in the polymer from strain 8191, or of trisaccharide residues in that from strain 39, although no traces of these were detected in partial, acid hydrolyzates. It does seem likely from analyses, however,... 

The preparation of trisaccharide 63 illustrates the activation and enzymic coupling of the 9-acetate of vV-acetylneuraminic acid, This involves the utilization of enzymes in a cascade of reactions which probably do not occur in cells (a) synthesis of Neu5,9Ac2 from the 6-acetate of vV-acetylmannosa-mine with the catabolic sialyl aldolase, (b) activation with CMPNeu5Ac synthetase, and (c) coupling. Acetylation in cells seems posterior to coupling. Terminal nonreducing vV-acetyl-9-O-acetylneuraminic acid residues appear... 

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