Modular Synthesis of 5-Substituted Thiophen-2-yl <i>C</i>-2′-Deoxyribonucleosides
作者:Jan Bárta、Radek Pohl、Blanka Klepetářová、Nikolaus P. Ernsting、Michal Hocek
DOI:10.1021/jo800177y
日期:2008.5.1
A new modular methodology of preparation of 5-substituted thiophene-2-yl C-nucleosides was developed. A Friedel−Crafts-type of C-glycosidation of 2-bromothiophene with toluoyl-protected methylglycoside 2 gave the desired protected 1β-(5-bromothiophen-2-yl)-1,2-dideoxyribofuranose 4a in 60%. The key intermediate 4a was then subjected to a series of palladium-catalyzed cross-coupling reactions. The cross-coupling
开发了一种新的制备5-取代的噻吩-2-基C-核苷的模块化方法。弗里德尔-克拉夫茨型2-溴噻吩与对甲苯甲酰基保护的甲基苷的C-糖苷化的2得到所需保护的1β-(5-溴噻吩-2-基)-1,2- dideoxyribofuranose 4A在60%以上。然后使关键中间体4a经历一系列钯催化的交叉偶联反应。与烷基有机金属的交叉偶联反应得到β-(5-烷基噻吩-2-基)-2-脱氧核糖核苷4和7产量中等,伴有减少的副产品。另一方面,与芳基斯坦酮的交叉偶联进展顺利,以高收率得到一系列β-(5-芳基噻吩-2-基)-2-脱氧核糖核苷4。NaMeOH在MeOH中对甲苯甲酰化核苷的脱保护,以及Et 3 N·3HF对甲硅烷基化的核苷的脱保护得到一系列游离的C-核苷6。或者,通过未保护的1β-(5-溴噻吩-2-基)-1,2-二脱氧核糖呋喃糖与硼酸的水相交叉偶联反应,一步制备其它类型的5-芳基噻吩C-核苷6。标题5-芳基噻吩C-核苷6