Instituto de Química Rosario (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Suipacha 531, 2000, Rosario, Argentina.
Org Biomol Chem. 2011 Apr 21;9(8):3020-5. doi: 10.1039/c1ob00021g. Epub 2011 Mar 7.
Both anomers of the methyl glycoside of 6-O-benzyl-N-dimethylmaleoyl-D-allosamine (6 and 7) are glycosylated exclusively on O3 when reacting with the trichloroacetimidate of peracetylated α-D-galactopyranose (5). This regioselectivity is expected for 6, the α-anomer, as a strong hydrogen bond of its H(O)3 with the carbonyl group of the dimethylmaleoyl group occurs, as shown by NMR temperature dependence. However, this hydrogen bond was not encountered experimentally for 7, the β-anomer. A DFT study of the energies implied in an analog of the glycosylation reaction charged intermediate has explained neatly this behavior, in terms of strong hydrogen bonds occurring at these charged intermediates. This approach explains both the experimental regioselectivities found for 6 and 7, but furthermore the calculations have shown a marked agreement with the regioselectivities found for other related compounds in the literature.
当与全乙酰化的α-D-半乳糖吡喃糖的三氯乙酰亚胺（5）反应时，6-O-苄基-N-二甲基马来酰基-D-阿洛糖胺（6 和 7）的甲基糖苷的两种差向异构体都仅在 O3 上发生糖苷化。对于 6（α-异构体），这种区域选择性是预期的，因为其 H（O）3 与二甲基马来酰基的羰基之间发生了强烈的氢键，如 NMR 温度依赖性所示。然而，对于 7（β-异构体），这种氢键并未在实验中遇到。对糖基化反应带电荷中间体的类似物的能量的 DFT 研究，根据在这些带电荷中间体中发生的强氢键，很好地解释了这种行为。该方法解释了 6 和 7 的实验区域选择性，但此外，计算结果与文献中其他相关化合物的区域选择性非常吻合。
