Two new conformationally restricted piperidinone PNA adenine monomers 12 and 13 have been synthesised using a stereoselective synthesis strategy analogous to a previously published strategy for pyrrolidinone analogues. In contrast to the pyrrolidinone case, epimerisation occurred during the final hydrolysis step. However, the diastereomeric mixture could be separated by RP-HPLC to give small amounts of pure 12 and 13. These were built into a PNA dodecamer (once in a central position), and the thermal stability (Tm) of the modified oligomers hybridised to complementary DNA, RNA and PNA were measured. PNA modified with either 12 or 13 resulted in a decrease of the Tm compared to unmodified PNA and to pyrrolidinone modified PNA. Thus, any preorganisation for duplex formation of PNA with a six-membered piperidinone ring seems to be inferior to preorganisation with a five-membered ring in the pyrrolidinone PNA analogues studied earlier.
我们采用立体选择性合成策略合成了两种新的构象受限的
哌啶酮 PNA
腺嘌呤单体 12 和 13,该策略类似于之前发表的
吡咯烷
酮类似物的合成策略。与
吡咯烷酮的情况不同的是,在最后的
水解步骤中发生了二聚反应。不过,非对映异构体混合物可以通过 RP-HPLC 分离出来,得到少量纯的 12 和 13。将这些物质加入
PNA 十二聚体(一次位于中心位置),并测量了与互补 DNA、RNA 和
PNA 杂交的修饰寡聚体的热稳定性(Tm)。与未修饰的
PNA 和
吡咯烷酮修饰的
PNA 相比,用 12 或 13 修饰的
PNA 会降低 Tm。因此,在先前研究的
吡咯烷酮
PNA 类似物中,任何具有六元
哌啶酮环的
PNA 双链形成预组织似乎都不如具有五元环的预组织。