Monosaccharides with a cis-configuration at C-2 and -3 readily undergo inversion at C-2 in an acetolysis medium composed of acetic acid, acetic anhydride, and sulfuric acid. The acetolysis-inversion reaction has been carried out with 2,3;5,6-di-O-isopropylidene-D-gulofuranose, 2,3;6,7-di-O-isopropylidene-D-glycero-D-gulo-heptose, 2,3-O-isopropylidene-D-ribose, D-ribose, and D-mannose using chromatography for isolation of the deacetylated epimeric products. The reaction requires a medium with a high concentration of acetic acid (ca. 90%) and appears to take place only with furanose structures. Inversions observed with the unsubstituted pyranoses D-ribose and D-mannose probably occur because of tautomerization to furanose forms. The epimerization proceeds in the direction which yields a smaller number of cis-oriented groups at C-2, -3, and -4 of the furanose forms of monosaccharides.
在C-2和-3位置具有顺式构型的单糖在由乙酸、乙酸酐和硫酸组成的乙酰化介质中很容易在C-2位置发生倒位反应。使用色谱法分离去乙酰化的对映产物,已经对2,3;5,6-二-O-异丙基-D-古洛呋喃糖、2,3;6,7-二-O-异丙基-D-甘露-D-古庚糖、2,3-O-异丙基-D-核糖、D-核糖和D-甘露糖进行了乙酰化-倒位反应。该反应需要含有高浓度乙酸(约90%)的介质,并且似乎只发生在呋喃糖结构中。未取代的吡喃糖D-核糖和D-甘露糖观察到的倒位可能是因为互变异构为呋喃糖形式。对映异构化朝着使单糖呋喃糖形式的C-2、-3和-4位置具有较少顺式取向基团的方向进行。