- Silicon-29 NMR Spectroscopy in Carbohydrate Chemistry: Galactose Derivatives
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29Si NMR spectra of the O-trimethylsilyl (OTMS) derivatives of various methyl α- and β-D-galactopyranosides have been recorded.The effect of changes in the anomeric configuration provides a means of assigning the resonance of the 2-OTMS substituent.Whereas the signal of the OTMS group attached at the 6-position can be assigned readily, those of the OTMS group at the 3- or 4-position cannot be assigned unequivocally.
- Gale, D.J.,Evans, N.A.
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- Characterization of ulvan extracts to assess the effect of different steps in the extraction procedure
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An effective application development of the polysaccharide ulvan requires a comprehensive knowledge about the influence of the extraction process on composition of the extracts and in ulvan itself. In this context, the two main objectives of the present work are (1) the establishment of an efficient extraction process for ulvan and (2) development of an accurate characterization methodology to evaluate the extract composition and ulvan content. Three ulvan-rich extracts obtained by different schemes of extraction were studied. The methodology for the analysis was improved and a detailed analysis of extracted ulvan was provided. The polysaccharide is rich in ulvanobiuronic acid 3-sulfate type A [→4)-β-d-GlcAp-(1 → 4)-α-l-Rhap 3S-(1→], with minor amounts of ulvanobiuronic acid 3-sulfate type B [→4)-α-l-IdoAp-(1 → 4)-α-l-Rhap 3S-(1→]. The extract with the higher degree of purification is a high molecular weight polysaccharide (790 kDa) composed of rhamnose (22.4%), glucuronic acid (22.5%), xylose (3.7%), iduronic acid (3.1%) and glucose (1.0%). It is highly sulfated (32.2%) and contains 1.3% of proteins and 10.3% of inorganic material. Applying simple extraction scheme it was possible to obtain an extract from green algae with high content of ulvan without affecting the overall chemical structure of the polysaccharide.
- Costa, Carina,Alves, Anabela,Pinto, Paula R.,Sousa, Rui A.,Borges Da Silva, Eduardo A.,Reis, Rui L.,Rodrigues, Alírio E.
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experimental part
p. 537 - 546
(2012/06/15)
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- Ectyoceramide, the first natural hexofuranosylceramide from the marine sponge Ectyoplasia ferox
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Ectyoceramide (1a), a unique monoglycosylceramide with a galactose in the furanose form, was isolated from Ectyoplasia ferox, and its structure was determined by NMR spectroscopy, multiple tandem mass spectrometry, and chemical degradation. Ectyoceramide is the first example of a monohexofuranosylceramide and, more generally, the first natural glycosphingolipid with its first sugar in the furanose form.
- Costantino, Valeria,Fattorusso, Ernesto,Imperatore, Concetta,Mangoni, Alfonso
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p. 1433 - 1437
(2007/10/03)
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- A convenient method for the cleavage of the D-mannosyl-L-gulose disaccharide from bleomycin-A2.
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In order to elucidate the biological role of the sugar residue of the antitumor drug bleomycin, this was deglycosylated by beta-elimination under mild alkaline conditions, and by solvolysis with hydrogen fluoride. The latter procedure proved to be better because it led to the complete deglycosylation without modification of the peptide, thus allowing further biological investigations of this component.
- Kenani,Lamblin,Henichart
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- An Efficient Synthesis of Anhydroalditols and Allyl C-Glycosides
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Efforts to expedite production of anhydroalditols have led to a new, efficient synthesis of these compounds from alkyl glycosides.Silylation of the glycoside followed by reductive cleavage in the presence of triethylsilane and trimethylsilyl trifluoromethanesulfonate were carried out in the same reaction flask.Subsequent aqueous workup gave excellent yields of anhydroalditol(s).In some cases ring contraction was observed, but the use of bulkier silyl protecting groups gave greater yields of the expected product.This method was also shown to be an efficient means to prepare allyl C-glycosides, without any independent protecting or activating step, by simply replacing triethylsilane with allyltrimethylsilane in the synthetic scheme.
- Bennek, John A.,Gray, Gary R.
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p. 892 - 897
(2007/10/02)
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