Forsman Jonas J, Wärnå Johan, Murzin Dmitry Yu, Leino Reko
Laboratory of Organic Chemistry, Abo Akademi University, Abo, Finland.
Carbohydr Res. 2009 Jun 12;344(9):1102-9. doi: 10.1016/j.carres.2009.02.031. Epub 2009 Mar 10.
The mechanism of the acid-catalyzed anomerization of 1-O-acetyl-2,3,5-O-benzoyl-alpha- and -beta-L-ribofuranoses in different acetic acid-acetic anhydride mixtures was investigated. The progress of the reactions was followed by NMR spectroscopy and the rate constants for the reactions were determined by the use of a kinetic model. The site of anomeric activation was clarified by the use of (13)C-labeled acetic acid and acetic anhydride, respectively, proving that the anomerization takes place by exocyclic C-O cleavage, thus ruling out anomerization via acyclic intermediates. The role of the acetyl cation as the catalytically active species was further verified.
研究了在不同乙酸 - 乙酸酐混合物中1 - O - 乙酰基 - 2,3,5 - O - 苯甲酰基 - α - 和 - β - L - 呋喃核糖酸催化变旋的机理。通过核磁共振光谱跟踪反应进程，并使用动力学模型确定反应速率常数。分别使用(13)C标记的乙酸和乙酸酐阐明了异头碳活化位点，证明变旋是通过环外C - O键断裂发生的，从而排除了通过无环中间体进行变旋的可能性。进一步验证了乙酰阳离子作为催化活性物种的作用。
