A Stepwise Solvent-Promoted S<sub>N</sub>i Reaction of α-<scp>d</scp>-Glucopyranosyl Fluoride: Mechanistic Implications for Retaining Glycosyltransferases
作者:Jefferson Chan、Ariel Tang、Andrew J. Bennet
DOI:10.1021/ja209339j
日期:2012.1.18
labeled α-d-glucopyranosyl fluorides. The measured KIEs for the C1 deuterium, C2 deuterium, C5 deuterium, anomeric carbon, ring oxygen, O6, and solvent deuterium are 1.185 ± 0.006, 1.080 ± 0.010, 0.987 ± 0.007, 1.008 ± 0.007, 0.997 ± 0.006, 1.003 ± 0.007, and 1.68 ± 0.07, respectively. The transition state for the solvolysis reaction was modeled computationally using the experimental KIE values as constraints
α-d-吡喃葡萄糖基氟在六氟-2-丙醇中的溶剂分解得到两种产物,1,1,1,3,3,3-六氟丙-2-基α-d-吡喃葡萄糖苷和1,6-脱水-β- D-吡喃葡萄糖。对于在 56 到 100 °C 之间进行的反应,这两种产物的比率基本不变。溶剂分解反应的活化参数如下:ΔH(++) = 81.4 ± 1.7 kJ mol(-1),ΔS(++) = -90.3 ± 4.6 J mol(-1) K(-1)。为了表征,通过使用多重动力学同位素效应 (KIE) 测量,六氟-2-丙醇中溶剂分解反应的 TS,我们合成了一系列同位素标记的 α-d-吡喃葡萄糖基氟化物。C1 氘、C2 氘、C5 氘、异头碳、环氧、O6 和溶剂氘的测量 KIE 为 1.185 ± 0.006、1.080 ± 0.010、0.987 ± 0.007、1.009、0.07 ± 0.06 ± 分别为 003 ± 0.007 和 1.68 ±