The structure of ammocidin, a new apoptosis inducer in Ras-dependent cells from Saccharothnx sp. AJ9571, was elucidated to be as shown in Fig. 1 by NMR and degradation studies. Ammocidin consists of a 20-membered macrolide ring and three deoxy sugars identified as 6-deoxy-L-glucose, D-digitoxose and D-olivomycose.
Catalytic and Regioselective Oxidation of Carbohydrates To Synthesize Keto-Sugars under Mild Conditions
作者:Wataru Muramatsu
DOI:10.1021/ol502344h
日期:2014.9.19
A new catalytic and regioselective approach for the synthesis of keto-sugars is described. An organotin catalyst, Oc2SnCl2, in the presence of trimethylphenylammonium tribromide ([TMPhA](+)Br3(-)) accelerates the regioselective oxidation at the "axial"-OH group of 1,2-diol moieties in galactopyranosides. The reaction conditions can also be used for the regioselective oxidation of various carbohydrates.
Selective Axial-to-Equatorial Epimerization of Carbohydrates
作者:Hayden M. Carder、Yong Wang、Alison E. Wendlandt
DOI:10.1021/jacs.2c04743
日期:2022.7.6
Radical-mediated transformations have emerged as powerful methods for the synthesis of rare and unnatural branched, deoxygenated, and isomeric sugars. Here, we describe a radical-mediated axial-to-equatorial alcohol epimerization method to transform abundant glycans into rare isomers. The method delivers highly predictable and selective reaction outcomes that are complementary to other sugar isomerization
自由基介导的转化已成为合成稀有和非天然支链、脱氧和异构糖的有效方法。在这里,我们描述了一种自由基介导的轴向到赤道醇差向异构化方法,可将丰富的聚糖转化为稀有异构体。该方法提供高度可预测和选择性的反应结果,与其他糖异构化方法互补。异构体相互转化的合成效用通过方便的聚糖合成展示,包括一步糖多样化。机理研究表明,位点选择性和非对映选择性都是通过赤道位置的 α-羟基 C-H 键的高选择性 H 原子提取来实现的。