Separation of trimethylsilyl ethers of methyl(methyl 4-deoxy-O-methyl-β- l- threo-hex-4-enopyranosid)uronate by gas chromatography

Abstract

may be found among the products of the methylation of D-glucuronic or D-galacturonic acid conjugates’-3. This class of substance is formed by p-elimination reactions of esterified uranic acid derivatives under alkaline4-6 and neutral conditions’ and may also be formed by the action of certain enzymes 8 *O. Elimination reactions in uranic acids have been extensively studied”-l4 and it can be concluded that this type of reaction is a general means of degradation of heteropolysaccharides and poly(hexopyranosid)uronates in nature. As a result of /I-elimination in hexuronic acids, the asymmetric centre at C4 is no longer present and, therefore, the same olefins are formed from D-glucuronic and D-galacturonic acid derivatives. The separation of O-methyl derivatives of methyl(methy1 a-D-glucopyranosid)uronate has been described earlier’“. In this paper, we describe the separation of methyl(methyl 2,3,4-tri-O-methyl-a-D-glucopyranosid)uronate (1) and methyl (methyl 2,3,4-tri-0-methyl-a-D-galactopyranosid)uronate (2) in admixture with differently substituted olefinic saccharides (3-6). In view of the possibility of determining the number and the location of the methyl groups in the derivatives of methyl 4-deoxy-P-L-rhreo-hex-4-enopyranosiduronic acid by mass spectrometry lb, this work is a contribution to the analysis and unequivocal identification of compounds l-6 by combined gas chromatography-mass spectrometry (GC-MS).