Tetra-saccharides

Ford, L., et al., 1974. Cry.stal. structure of a ly.sozyme-tetra.saccharide lactone complex. y(9wm z/ of Molecular Biology 88 349-371. 

In contrast to L-iduronic acid residues, most of which are sulfated at C-2, D-glucuronic acid residues in heparin and heparan sulfate are largely or exclusively nonsulfated. This was especially proved by their susceptibility to periodate oxidation,123 and through characterization of D-glucuronic acid-containing di- and tetra-saccharides from deamina-tive104 109 110 138 or heparinase - heparanase cleavage137,145 of heparin. 

The conformational behaviour in solution of a dermatan-derived tetra-saccharide has been explored by means of NMR spectroscopy, especially by NOE-based conformational analysis. RDCs were also measured for the tetrasaccharide in a phage solution and interpreted in combination with restrained MD simulations. The RDC-derived data substantially confirmed the validity of the conformer distribution resulting from the NOE-derived simulations, but allowed an improved definition of the conformational behaviour of the oligosaccharides in solution, which show a moderate flexibility at the central glycosidic linkage. Differences in the shapes of the different species with the IdoA in skew and in chair conformations and in the distribution of the sulphate groups were also highlighted.28... 

Taken as a whole, the results indicate that the amylase of Aspergillus oryzae causes the rapid random hydrolysis both of the straight and of the branched chain components of starch and that it hydrolyzes very slowly products with average molecular weights of penta- and tetra-saccharides. 

Scammonin VIII (104), isolated from Convulvulus scammonia, is a linear tetra-saccharide of jalapinolic acid with two glucoses, one rhamnose, and one quinovose. This compound represents the only macrocyclic resin glycoside of scammonic acid B (hexadecanoic acid, (115)-[(0-jS-D-glucopyranosyl-(l—>4)-0-6-deoxy-a-L-man-nopyranosyl-(1 2)-0- S-D-glucopyranosyl-(l- 2)-6-deoxy- S-D-glucopyranosyl)oxy]). 

The original publication by Sweeley and coworkers5 was concerned with the separation of a wide range of carbohydrates, from mono- to tetra-saccharides. Most of the subsequent publications have considered the quantitative analysis of mixtures of varied complexity, although two studies have demonstrated the separation of the protium from the deuterium fonns of monosaccharides.200,201 The study of mutarotational equilibria by gas-liquid chromatography has been discussed in Section IV (see p. 38). 

In model studies,224,225 oligosaccharides have been separated as their trifluoroacetates, and Vilkas and coworkers224 found that a tetra-saccharide so esterified had a retention time of six minutes at 250°. Similar results were obtained by Nakamura and Tamura,49 who showed that, on a column of OV-1 at 220°, the retention time of per-0-(trimethylsilyl)sucrose was 12 min, whereas, at 140°, the per(tri-fluoroacetate) required only 7 min. Other comparative data were provided for the common disaccharide alditols. A study of the concentration of lactose in blood was made by using this method 48 it was also shown48 that trifluoroacetylation of disaccharides proceeds more rapidly and satisfactorily in N,N-dimethylformamide than in ethyl acetate. 

Mannose tri-, tetra- and pentasaccharide together with GM1 octasaccharide were a gift from Dr. M.A. Chester (Lund, Sweden). At the time of writing, these standards are no longer available. Pentasaccharides (from human urine) and sialylated tetra-saccharides (from human milk) are available from Sigma however, they are cost-prohibitive for routine use. 

The potential of the negative chemical-ionization (n.c.i.) technique for obtaining valuable structural information on very small samples of underivatized oligosaccharides has been demonstrated.200 The n.c.i. spectra of several mono-, di-, tri-, and tetra-saccharides were recorded, using methane as the reagent gas, and direct-probe insertion of the samples into the ion source.201 Fairly intense, molecular ions, M-, were observed in each case. A small number of fragment ions were also observed, but could not be interpreted. Use of dichlorodifluoro-... 

In all of the syntheses of tri- and tetra-saccharides thus far described, emanating from several different laboratories, fucosylation was performed on a suitably protected nucleophile. A bromide of a fu-cose-containing disaccharide was not prepared, although use of such a compound would be feasible in principle, as was shown in one case of a synthetic glycoside (see later). 

H. Paulsen, R. Wilkens, F. Reck, and I. Brockhausen, Synthese von verzweigten Tetra-saccharid- und Pentasacchaiid-Strukiurene von W-Glycoprotein, Methyliert and 4 -OH des Vezweigungsgliedes, Liebigs Ann. Chem. 1303 (1992). 

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,... 

Early work on heparin and heparan sulfate was mainly concerned with isolation and identification of di- and tetra-saccharides. The main product of heparin lyase action on bovine-liver heparin was276 the unsaturated,... 

The details of the synthetic approach we have adopted for the preparation of all possible di- and trisaccharide sequences of the Y polysaccharide repeating unit have been published (16-19), together with the syntheses of two of the four possible tetrasaccharides (19,20). The synthesis of a third tetra-saccharide sequence not previously reported is described below. 

The a,l ->4-linked bis-digitoxoside 208 after treatment with triethyl orthoacetate and subsequent acetylation, gives both the diastereomeric orthoester intermediates 209. Acid-catalyzed 3, 4 -orthoacetate opening leads to both the 3, 3 - and the 3,4 -diacetates 210 and 211 in the ratio 3 1. NIS glycosylation of 210 with digilanidobial 206 furnished the central a, l- 4-linkage in 212, and following reduction the tetra-saccharide species 213 results [107]. 

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