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| Natura: | Artículo científico |
| Lingua: | en |
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Academia Brasileira de Ciências
2005
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| Accesso online: | https://www.redalyc.org/articulo.oa?id=32777203 |
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| _version_ | 1866556987419918336 |
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| author | Marcello Iacomini |
| author_facet | Marcello Iacomini |
| contents | Methylation-GC-MS analysis of arabinofuranose- and galactofuranose-containing structures: rapid synthesis of partially O-methylated alditol acetate standards Marcello Iacomini Philip A.J. Gorin Guilherme L. Sassaki Multidisciplinaria (Ciencias Naturales y Exactas) GC NMR partially O MS standards OH reactivity Arabinose and galactose were treated with MeOH containing traces of H2SO4 or HCl at 25◦C to give mixtures of their methyl alpha-andbeta-furanosides, as shown by 1D and 2D nuclear magnetic resonance (NMR). Oxidation of the Me alpha, beta-Ara f mixture with NaIO4 preferentially oxidized the beta-isomer, to give pure Me alpha-Ara f. Each product was progressively O-methylated using the Purdie reagent (MeI/Ag2O) at 25◦C and resulting mixtures of partially methylated glycosides (PMGs) were rapidly assayed by thin layer chromatography (TLC) first to favour higher yields of mono-O-methyl derivatives and later for products with higher degrees of methylation. The products were converted to complex mixtures of partially O-methylated alditol acetate derivatives (PMAAs) by successive hydrolysis, reduction with NaBD4, and acetylation. These can be used as gas chromatography-mass spectrometry (GC-MS) standards in methylation analysis of complex carbohydrates containing arabinofuranosyl and galactofuranosyl units. Of particular interest were the retention times and electron impact MS of the difficult to prepare alditol acetates of 5,6-Me2Gal,2,5-Me2Gal,2,5,6-Me3Gal,3,5,6-Me3Gal,5-MeAra,2,5-Me2Ara, and 3,5-Me2Ara. The relative reactivities of hydroxyl groups for mixtures of Me alpha- and Me beta-Galf wereHO-2>HO-3>HO-6>HO-5,that of Me alpha-and Me beta-Ara f HO-2>HO-3>HO-5,and that of Me alpha-Ara f HO-2>HO-3≥HO-5.Partially O-methylated alditol acetates, GC-MS standards, Purdie methylation, OH reactivity, NMR. 2005 artículo científico 0001-3765 https://www.redalyc.org/articulo.oa?id=32777203 en http://www.redalyc.org/revista.oa?id=327 Anais da Academia Brasileira de Ciências application/pdf Academia Brasileira de Ciências Anais da Academia Brasileira de Ciências (Brasil) Num.2 Vol.77 |
| format | Artículo científico |
| id | redalyc_32777203 |
| language | en |
| publishDate | 2005 |
| publisher | Academia Brasileira de Ciências |
| spellingShingle | Methylation-GC-MS analysis of arabinofuranose- and galactofuranose-containing structures: rapid synthesis of partially O-methylated alditol acetate standards Marcello Iacomini Multidisciplinaria (Ciencias Naturales y Exactas) GC NMR partially O MS standards OH reactivity Methylation-GC-MS analysis of arabinofuranose- and galactofuranose-containing structures: rapid synthesis of partially O-methylated alditol acetate standards Marcello Iacomini Philip A.J. Gorin Guilherme L. Sassaki Multidisciplinaria (Ciencias Naturales y Exactas) GC NMR partially O MS standards OH reactivity Arabinose and galactose were treated with MeOH containing traces of H2SO4 or HCl at 25◦C to give mixtures of their methyl alpha-andbeta-furanosides, as shown by 1D and 2D nuclear magnetic resonance (NMR). Oxidation of the Me alpha, beta-Ara f mixture with NaIO4 preferentially oxidized the beta-isomer, to give pure Me alpha-Ara f. Each product was progressively O-methylated using the Purdie reagent (MeI/Ag2O) at 25◦C and resulting mixtures of partially methylated glycosides (PMGs) were rapidly assayed by thin layer chromatography (TLC) first to favour higher yields of mono-O-methyl derivatives and later for products with higher degrees of methylation. The products were converted to complex mixtures of partially O-methylated alditol acetate derivatives (PMAAs) by successive hydrolysis, reduction with NaBD4, and acetylation. These can be used as gas chromatography-mass spectrometry (GC-MS) standards in methylation analysis of complex carbohydrates containing arabinofuranosyl and galactofuranosyl units. Of particular interest were the retention times and electron impact MS of the difficult to prepare alditol acetates of 5,6-Me2Gal,2,5-Me2Gal,2,5,6-Me3Gal,3,5,6-Me3Gal,5-MeAra,2,5-Me2Ara, and 3,5-Me2Ara. The relative reactivities of hydroxyl groups for mixtures of Me alpha- and Me beta-Galf wereHO-2>HO-3>HO-6>HO-5,that of Me alpha-and Me beta-Ara f HO-2>HO-3>HO-5,and that of Me alpha-Ara f HO-2>HO-3≥HO-5.Partially O-methylated alditol acetates, GC-MS standards, Purdie methylation, OH reactivity, NMR. 2005 artículo científico 0001-3765 https://www.redalyc.org/articulo.oa?id=32777203 en http://www.redalyc.org/revista.oa?id=327 Anais da Academia Brasileira de Ciências application/pdf Academia Brasileira de Ciências Anais da Academia Brasileira de Ciências (Brasil) Num.2 Vol.77 |
| title | Methylation-GC-MS analysis of arabinofuranose- and galactofuranose-containing structures: rapid synthesis of partially O-methylated alditol acetate standards |
| topic | Multidisciplinaria (Ciencias Naturales y Exactas) GC NMR partially O MS standards OH reactivity |
| url | https://www.redalyc.org/articulo.oa?id=32777203 |