Del Vigo Enrique A, Stortz Carlos A, Marino Carla
Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Consejo Nacional de Investigaciones Científicas y Técnicas, Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR), Departamento de Química Orgánica, Pab. 2, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
Beilstein J Org Chem. 2019 Dec 19;15:2982-2989. doi: 10.3762/bjoc.15.294. eCollection 2019.
Regioselective glycosylations allow planning simpler strategies for the synthesis of oligosaccharides, and thus reducing the need of using protecting groups. With the idea of gaining further understanding of such regioselectivity, we analyzed the relative reactivity of the OH-3 and OH-4 groups of 2,6-diprotected methyl α- and β-galactopyranoside derivatives in glycosylation reactions. The glycosyl acceptors were efficiently prepared by simple methodologies, and glycosyl donors with different reactivities were assessed. High regioselectivities were achieved in favor of the 1→3 products due to the equatorial orientation of the OH-3 group. A molecular modeling approach endorsed this general trend of favoring O-3 substitution, although it showed some failures to explain subtler factors governing the difference in regioselectivity between some of the acceptors. However, the Gal-(β1→3)-Gal linkage could be regioselectively installed by using some of the acceptors assayed herein.
区域选择性糖基化反应有助于设计更简单的寡糖合成策略，从而减少保护基团的使用。为了进一步了解这种区域选择性，我们分析了2,6 - 二保护的甲基α - 和β - 吡喃半乳糖苷衍生物的OH - 3和OH - 4基团在糖基化反应中的相对反应活性。通过简单的方法高效制备了糖基受体，并评估了具有不同反应活性的糖基供体。由于OH - 3基团的平伏键取向，实现了有利于1→3产物的高区域选择性。分子建模方法支持了这种有利于O - 3取代的总体趋势，尽管它在解释一些受体之间区域选择性差异的更细微因素方面存在一些不足。然而，通过使用本文测定的一些受体，可以区域选择性地安装Gal-(β1→3)-Gal连接。
