Department of Chemistry , Emory University , Atlanta , Georgia 30322 , United States.
Org Lett. 2019 May 3;21(9):3295-3298. doi: 10.1021/acs.orglett.9b01024. Epub 2019 Apr 23.
This work characterizes a previously undetected epimerization in the preparation of alkynyl diols from pentose precursors utilizing the Ohira-Bestmann reagent. Lithium trimethylsilyldiazomethane (Colvin reagent) additions to the d-ribose and d-lyxose-derived benzylidene acetals provide the respective alkynyl diol stereoisomers, without epimerization. Regioselective tungsten-catalyzed cycloisomerizations of the d-ribose- and d-lyxose-derived alkynyl diols yield rigid bicyclic pyranose glycals, confirming the stereochemical fidelity of the Colvin alkynylation process.
这项工作描述了在使用 Ohira-Bestmann 试剂从戊糖前体制备炔二醇时,以前未检测到的差向异构化。三甲基硅基锂重氮甲烷(科尔文试剂)加成到 d-核糖和 d-木糖衍生的亚苄基缩醛中,提供了各自的炔二醇立体异构体,没有差向异构化。区域选择性钨催化的 d-核糖和 d-木糖衍生的炔二醇的环异构化反应生成刚性双环吡喃糖糖醛,证实了科尔文炔基化反应过程的立体化学保真度。