Shadrick Melanie, Yu Charlene, Geringer Scott, Ritter Sean, Behm Alexanndra, Cox Abby, Lohman Matt, De Meo Cristina
Department of Chemistry Southern Illinois University Edwardsville, 1 Hairpin Dr., Edwardsville, IL 62025, USA.
New J Chem. 2018 Sep 7;42(17):14138-14141. doi: 10.1039/C8NJ02795A. Epub 2018 Jul 17.
The stereoselective synthesis of sialic acid glycoconjugates is still a challenge in the field. Surprisingly, little is known on the regioselective O-substitution of sialic acids. Consequently, the effect of O-protecting groups and/or regioselectively protected building blocks in sialylations, remains practically unexplored. O-Picoloyl protecting groups have emerged as novel substituents that have a profound effect on sialylations. Recently, high stereoselectivities were obtained by introducing picoloyl groups at the C-4 and C-7/C-8 positions. However, to understand the relationship between the position of the picoloyl group and its exact effect in sialylations, a convenient access to a wider range of regioselectively picoloylated building blocks is needed. Reported herein is a new method that provides an accessible route to a wide array of regioselectively acylated building blocks. The regioselective introduction of picoloyl groups at various O-positions was achieved either by controlled direct picoloylation or by applying a modified ReSET methodology.
唾液酸糖缀合物的立体选择性合成仍是该领域的一项挑战。令人惊讶的是，关于唾液酸的区域选择性O-取代知之甚少。因此，O-保护基和/或区域选择性保护的结构单元在唾液酸化反应中的作用实际上仍未得到探索。O-吡啶甲酰基保护基已成为对唾液酸化反应有深远影响的新型取代基。最近，通过在C-4和C-7/C-8位引入吡啶甲酰基获得了高立体选择性。然而，为了理解吡啶甲酰基的位置与其在唾液酸化反应中的确切作用之间的关系，需要一种方便的方法来获得更广泛的区域选择性吡啶甲酰化结构单元。本文报道了一种新方法，该方法为多种区域选择性酰化结构单元提供了一条可行的途径。通过可控的直接吡啶甲酰化或应用改良的ReSET方法，实现了在各种O-位区域选择性引入吡啶甲酰基。
