Mercaptolyse du 2-acétamido-3-O-(D-1-carboxyéthyl)- 2-désoxy-D-glucose (acide N-acétylmuramique)
作者:Alain Veyrières
DOI:10.1016/s0008-6215(00)82797-4
日期:1974.4
ethanethiol and hydrochloric acid gave a mixture of the acyclic dithioacetal ( 2 ) and the corresponding internal ester. After substitution of the hydroxyl and carboxyl groups, the dithioacetal was transformed into the dimethyl acetal ( 5 ) by treatment with mercuric oxide and boron trifluoride etherate in anhydrous methanol. Removal of the O -acetyl group with sodium methoxide afforded 2-acetamido-2-deoxy-5
beta-D-Galactopyranosyl-(1 -> 3)-2-acetamido-2-deoxy-D-glucose (LNB) and beta-D-galactopyranosyl-(1 -> 3)-2-acetamido-2-deoxy-D-galactose (GNB) decompose rapidly upon heating into D-galactose and mono-dehydrated derivatives of the corresponding 2-acetamido-2-deoxy-D-hexoses, including 2-acetamido-2,3-dideoxy-hex-2-enofuranoses and bicyclic 2-acetamido-3,6-anhydro-2-deoxy-hexofuranoses. The decomposition is conducted under neutral conditions where glycosyl linkages are generally believed to be stable. The half-lives of LNB and GNB were 8.1 min and 20 min, respectively, at 90 degrees C and pH 7.5. The pH dependency of decomposition rates suggests that the instabilities are an extension of the conditions for the peeling reaction, often observed with glycans of O-linked glycoproteins under alkaline conditions. Such decomposition under the neutral conditions is commonly observed with 3-O-linked reducing aldoses. (C) 2010 Elsevier Ltd. All rights reserved.