Department of Pharmaceutical and Biomedical Sciences, University of Georgia, 250 West Green Street, Athens, Georgia 30602, United States.
Department of Chemistry, University of Georgia, 302 East Campus Road, Athens, Georgia 30602, United States.
J Org Chem. 2023 Mar 17;88(6):3678-3696. doi: 10.1021/acs.joc.2c02889. Epub 2023 Mar 6.
The use of a phenylthio group (SPh) as a dummy ligand at the 6-position to control the side-chain conformation of a series of hexopyranosyl donors is described. The SPh group limits side-chain conformation in a configuration-specific manner, which parallels that seen in the heptopyranosides, and so influences glycosylation selectivity. With both d- and l-glycero-d-galacto-configured donors, the equatorial products are highly favored as they are with an l-glycero-d-gluco donor. For the d-glycero-d-gluco donor, on the other hand, modest axial selectivity is observed. Selectivity patterns are discussed in terms of the side-chain conformation of the donors in combination with the electron-withdrawing effect of the thioacetal group. After glycosylation, removal of the thiophenyl moiety and hydrogenolytic deprotection is achieved in a single step with Raney nickel.
描述了在 6-位使用苯基硫基（SPh）作为虚拟配体来控制一系列己吡喃糖供体侧链构象的方法。SPh 基团以特定于构型的方式限制侧链构象，与庚吡喃糖苷相似，因此影响糖苷化选择性。对于 d-和 l-甘油-d-半乳糖构型的供体，与 l-甘油-d-葡萄糖供体一样，优先得到平伏产物。对于 d-甘油-d-葡萄糖供体，另一方面，观察到适度的轴向选择性。选择性模式根据供体侧链构象以及硫代缩醛基团的吸电子效应进行讨论。糖苷化后，通过雷尼镍可以在一步中同时去除硫苯基部分和氢解脱保护。
