Ekeberg Dag, Morgenlie Svein, Stenstrøm Yngve
Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, PO Box 5003, Norway.
Carbohydr Res. 2007 Oct 15;342(14):1992-7. doi: 10.1016/j.carres.2007.05.033. Epub 2007 Jun 7.
The reaction rate of the Lobry de Bruyn-Alberda van Ekenstein transformation of aldoses to ketoses in boiling pyridine was strongly increased by the addition of aluminium oxide. In addition to aldose-ketose transformation, 2-epimers of the starting aldoses and 3-epimers of the primarily produced ketoses were formed to some extent, as reported also when these reactions are carried out without aluminium oxide. The relative amounts of the primary ketose and the starting aldose in the reaction mixtures may be explained on the basis of their stability, predicted from reported free energy calculations. Isomerisation of ketoses to aldoses was much slower than the reverse reaction. The relative free energies are also in these cases important, the very stable xylo-2-hexulose gave only 7% and 6% of the aldoses gulose and idose, respectively, after boiling for 7h in pyridine in the presence of aluminium oxide.
在沸腾的吡啶中，通过添加氧化铝，醛糖向酮糖的洛布里·德布鲁因 - 阿尔贝达·范埃肯斯坦转化反应速率大幅提高。除了醛糖 - 酮糖转化外，起始醛糖的2 - 差向异构体和主要生成的酮糖的3 - 差向异构体也会在一定程度上形成，这与在不添加氧化铝的情况下进行这些反应时的报道情况相同。反应混合物中初级酮糖和起始醛糖的相对含量可以根据它们的稳定性来解释，这种稳定性是根据已报道的自由能计算预测的。酮糖向醛糖的异构化比逆反应慢得多。在这些情况下，相对自由能也很重要，非常稳定的木糖 - 2 - 己酮糖在氧化铝存在下于吡啶中煮沸7小时后，分别仅产生7%和6%的醛糖古洛糖和艾杜糖。
