5-methylcytosine) and purine (adenine, guanine) bases. The reaction was highly stereoselective, giving only a single dimeric species having the ribo-configuration of the newly introduced C-3'-branched methylene moiety. Also prepared were dimers 16, incorporating 2'-O-methyl ribonucleosides in both halves of the dimer. This required the synthesis of 3'-deoxy-3'-iodo-2'-O-methyl nucleosides 12 as well as 2'-O-me
由双(
三甲基锡烷基)苯并频哪酸酯(8)介导的烷基
碘和
肟的高度收敛性自由基偶联已被用于制备一系列二聚核苷,以模拟天然核酸。反应条件的系统优化允许将适当的
碘化物和
肟单步转化为中等至极好的收率的2'-脱氧二聚体9。例如,3'-脱氧-3'-
碘-5'-(三苯基甲基)
胸苷(6a)与3'-O-(叔丁基二苯基甲
硅烷基)-5'-O-(亚甲基亚
氨基)
胸苷(7a)的反应在8存在下,在脱气的苯中得到81%的3'-脱(氧膦)-3'-(亚甲基亚
氨基)-5'-O-(三苯甲基)
胸苷基-(3'-> 5')-3 -O-(叔丁基二苯基甲
硅烷基)
胸苷(9a)。同样制备的是含有
嘧啶(胸腺
嘧啶,5-甲基
胞嘧啶)和
嘌呤(
腺嘌呤,
鸟嘌呤)碱基的二聚体。该反应是高度立体选择性的,仅给出具有新引入的C-3'-支链亚甲基部分的
核糖构型的单个二聚体物质。还制备了二聚体16,在二聚体的两半中都掺入了2'-O-甲基
核糖核苷。这需要合成3'-脱氧-3