Pentasaccharides, methylation

An intramolecular acetal has also been introduced by the treatment of a mixture of a 1-thio-mannoside, having a methoxybenzyl protecting group at C-2 and an alcohol with DDQ [71] (Scheme 4.4c). Activation of the thioglycoside with methyl triflate gave a P-mannoside as the only anomer. This approach was employed for the synthesis of the core pentasaccharide of N-linked glycoproteins. 

Fig. 4 Stereo views (in transparent, space-filling models) of selected hydrophobic interactions in the Fab-peptide and -pentasaccharide complexes. A Trp P3 buried in the hydrophobic cavity formed by CDR L3, His H58 and Trp H47. B Interactions of the side chain of Met P5 with Trp H33. C and D Interactions of the peptide and pentasaccharide, respectively, with His L27D and Tyr L32 (the pocket which accommodates the GlcNAc D methyl group). In (C) the hydrogen bond between the Asp P2 side chain and His L27D NE2 is also shown. A corresponding hydrogen bond between Rha Al 3-OH and His L27D NE2, shown in (D), represents an element of structural mimicry. Reproduced from [80]. 2003 by The National Academy of Sciences of the USA...

Similarly, methylation analysis of a partially hydrolyzed sample of the Klebsiella type 38 capsular polysaccharide, composed of pentasaccharide repeating units (5), revealed that the terminal 3-deoxy-L-g/ycero-pentulosylonic acid group (6) was located at 0-3 of a D-galac-tosyl residue (7), as the 6-O-methyl-D-galactose in the methylation... 

The extracellular polysaccharides of Rhizobium meliloti 201 have been examined by using enzymic degradation and chemical procedures.314 A mixture of polysaccharides produced by the bacterium, when incubated with a bacterial enzyme that hydrolyzed one of these, gave oligosaccharides that could be separated by DEAE-cellulose chromatography. The major fraction was a pentasaccharide, for which methylation analysis and Smith... 

Ten sialic-acid-containing oligosaccharides and four neutral oligosaccharides have been purified from the major glycoprotein fraction of hog, submaxillary-gland mucin. H-N.m.r. spectroscopy at 360 MHz, in combination with methylation analysis and mass spectrometry, allowed the determination of their structures, which are partial structures of a pentasaccharide (see Fig. 42) having blood-group A activity.221... 

Figure 6. Preliminary methylation linkage analysis of the major pentasaccharide from tobacco glycophosphoceramide concentrate...

Two pentasaccharides occur in the mixture of milk oligosaccharides. Lacto-iV-fucopentaose I readily gives an alkali-stable disaccharide, 2-0-(a-L-fucosyl)-D-galactose on alkaline degradation knowledge of the structure of this disaccharide, together with data from methylation studies, leads to the assignment of the structure of an a-L-fucosyl-(lacto-iV-tetraose) for the pentasaccharide.273... 

Methyl 2-acetamido-2-deoxy-a-D-galactopyranoside was the best inhibitor tested.83,558,581 582 587 The observation that a blood-group Type A pentasaccharide inhibited to approximately the same extent as this glycoside led to the conclusion that the combining site accommodates a... 

A pentasaccharide and a trisaccharide have been isolated from an enzymic hydrolyzate of hemicellulosic material from oat coleoptiles.224 Methylation analysis of their structures indicated that these compounds may derive from j8-D-(l — 4)-linked D-glucans having terminal D-xylopyranosyl groups on some 0-6 atoms. Xylo-glucans having these structural features are present in the primary cell-walls of dicotyledons.22411... 

Paulsen, H, Wilkens, R, Brockhausen, I, Building units of oligosaccharides. CIV. Synthesis of branched tetrasaccharide and pentasaccharide structures of A-glycoproteins methylated at 4 -OH of the branching unit, Liebigs Ann. Chem., 1303-1313, 1992. 

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