Rapid synthesis of partially O-methylated alditol acetate standards for GC–MS: some relative activities of hydroxyl groups of methyl glycopyranosides on Purdie methylation

• Published in: Carbohydrate research 2005-03, Vol.340 (4), p.731-739
• Main Authors: Sassaki, Guilherme L., Gorin, Philip A.J., Souza, Lauro M., Czelusniak, Phelipe A., Iacomini, Marcello
• Format: Article
• Language: English
• Subjects: Acetates - chemical synthesis; Acetates - standards; Chromatography, Gas; GC–MS standards; Hydroxyl Radical - chemistry; Mass Spectrometry; Methylation; OH reactivity; Partially O-methylated alditol acetates; Polysaccharides - chemistry; Purdie methylation; Reference Standards; Sugar Alcohols - chemical synthesis; Sugar Alcohols - standards; Time Factors
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2005.01.020

[Display omitted] Mixtures containing the majority of partially O-methylated alditol acetates (PMAAs), necessary for the GC–MS based identification of glycosidic linkages in oligo- and polymeric structures were prepared. Rha, Fuc, Rib, Ara, Xyl, Man, Gal, and Glc were converted to their Me glycosides, and the products were progressively O-methylated using the Purdie reagent at 25 °C. Resulting PMGs were assayed by TLC and at times that were optimum for formation of mono- O-methyl derivatives and later for higher degrees of methylation; they were converted to PMAAs, in a process incorporating NaB 2H 4 reduction. The majority of these can be used as standards for simultaneous identification of pyranosides and some furanosyl units particularly in heteropolysaccharides. The relative reactivities of OH-groups were determined by GC–MS as: Me α- and β-Glc p, HO-2 > HO-4 > HO-3 > HO-6, Me α- and β-Gal p, HO-3 > HO-2 > HO-4 > HO-6, Me α-Man p, HO-3 > HO-2 > HO-4 > HO-6, Me β-Man p, HO-3 > HO-4 ⩾ HO-6 > HO-2, Me α-Rha p, OH-3 > OH-2 > OH-4; Me αβ-Fuc p, OH-2 > OH-3 > OH-4, and Me αβ-Xyl p, OH-2 > OH-4 > OH-3. The results differ from those obtained with Haworth, Hakomori, and Ciucanu methylation techniques, although some similarities occurred with the more rapid Kuhn method.