- Syntheses of 2,6-anhydroaldonic acids from the corresponding anhydrodeoxynitroalditols (glycopyranosylnitromethanes) and their conversion into methyl esters, amides, and alditols
-
2,6-Anhydroaldonic acids were obtained by oxidation of the corresponding anhydrodeoxynitroalditols (glycopyranosylnitromethanes) with hydrogen peroxide in alkaline solution. Purification was achieved via the methyl anhydroaldonates. The syntheses of five 2,6-anhydrohexonic and eight 2,6-anhydroheptonic acids were accomplished in yields of 44-81%. All corresponding unprotected and acetylated methyl 2,6-anhydroaldonates were characterised. Ammonolysis of the former afforded the corresponding amides in quantitative yields; reduction with sodium borohydride gave the analogous anhydroalditols. Copyright (C) 1998 Elsevier Science Ltd.
- Dromowicz, Manfred,Koell, Peter
-
-
Read Online
- Role of acid sites and selectivity correlation in solvent free liquid phase dehydration of sorbitol to isosorbide
-
A number of Br?nsted acids (methanesulfonic acid, p-toluene sulfonic acid, triflic acid, sulfamic acid, citric acid, NaHSO4, and boric acid) and Lewis acids (metal sulfate/triflates) were employed in solvent free dehydration of sorbitol and their influence on anhydroalcohols selectivity has been investigated. The outcome indicated that all the acid catalysts produced first mono-dehydrated product sorbitan followed by second dehydration of 1,4-sorbitan to isosorbide. However, the formation and yield isosorbide were found to depend on the nature of acid sites and their acidic strength. The Br?nsted acids are more efficient to convert sorbitol to isosorbide than Lewis acids. The Br?nsted acids having lower pKa value (i.e. strong acid) exhibited high catalytic activity as well as yield of isosorbide. In the case of Lewis acids, the catalytic activity and selectivity were radically depended on which metal used and their stability during the reaction. The water formed during reaction induced Br?nsted acidity on Lewis acid metal site. The Lewis-assisted Br?nsted acid site enabled high yield of isosorbide up to 70% at moderate temperature (160°C).
- Dabbawala, Aasif A.,Mishra, Dinesh K.,Huber, George W.,Hwang, Jin-Soo
-
p. 252 - 261
(2015/05/05)
-
- Synthesis of aromatic C-xylosides by position inversion of glucose
-
Two formally C-xylosylated analogs to 2-naphthyl β-d-xylopyranoside, which is known to initiate priming of glucosaminoglycan chains, were synthesized by a position inversion of glucose (i.e., position 1 becomes position 5). The d-C-xyloside showed priming, while the l-C-xyloside did not initiate priming.
- Malmberg, Jesper,Mani, Katrin,Saewen, Elin,Wiren, Anders,Ellervik, Ulf
-
p. 6659 - 6665
(2007/10/03)
-