Stereo- and Regioselective Introduction of 1- or 2-Hydroxyethyl Group via Intramolecular Radical Cyclization Reaction with a Novel Silicon-Containing Tether. An Efficient Synthesis of 4‘α-Branched 2‘-Deoxyadenosines<sup>1</sup>
作者:Satoshi Shuto、Makiko Kanazaki、Satoshi Ichikawa、Noriaki Minakawa、Akira Matsuda
DOI:10.1021/jo971703a
日期:1998.2.1
reaction gave the 4'alpha-(2-hydroxyethyl) derivative 21, via a 6-endo-radical cyclized product 20, as the sole product in 72% yield. The reaction of 17 in the presence of excess Bu(3)SnH gave 19 quantitatively, via a 5-exo-cyclized product 18, as a diastereomeric mixture. The reaction mechanism was examined using Bu(3)SnD. The results demonstrated that the 5-exo cyclized (3-oxa-2-silacyclopentyl)methyl
利用新型的与硅系链的自由基环化反应,已经开发出一种有效的方法,该方法可以从2'-脱氧腺苷开始合成4'α-支链的2'-脱氧腺苷。4'β-(苯基硒代)-3'-O-二苯基乙烯基甲硅烷基腺嘌呤核苷衍生物17与Bu(3)SnH和AIBN的自由基反应,然后经Tamao氧化,选择性地产生4'α-(2-羟乙基)衍生物21或4'α-(1-羟乙基)衍生物19,取决于反应条件。在较低的Bu(3)SnH浓度下,该反应通过6-内-自由基环化产物20以4%的收率得到了4'α-(2-羟乙基)衍生物21,其为唯一的产物。17在过量Bu(3)SnH存在下的反应通过5外环化产物18定量得到19,为非对映异构体混合物。使用Bu(3)SnD检查了反应机理。结果表明,最初形成了5-exo环化的(3-oxa-2-silacyclopentyl)甲基(C),当Bu(3)SnH(D)的浓度足够高时,该自由基被捕获。在较低浓度的Bu(3)