Chiral peptide nucleic acid (PNA) is a derivative of regular PNA by introducing a chiral center to its backbone, and is known to bind more strongly to DNA or RNA than regular PNA. In particular, in the case of a γ-backbone, the L isomer stabilizes the PNA/DNA duplex, and the D-isomer has the opposite effect. Therefore, the synthesis of an optically pure γ-backbone is very important. Here, we report a novel synthetic strategy for the suppression of epimerization during the synthesis of the γ-PNA backbone. A stabilized form of 2-iodoxybenzoic acid (SIBX) was used as an oxidative reagent in the key intermediate of the N-Boc-amino acetaldehyde synthesis. This paper reports (1) the synthesis and comparison of three different γ-PNA backbones (lysine, alanine, and glutamate) by three different synthetic routes (SIBX, lithium aluminum hydride, and Red-Al) and (2) the determination of chiral purity from their derivative compounds. The enantiomeric excess purity of SIBX-mediated γ-PNA backbones was determined to be more than 99.4%, as ascertained by the high-performance liquid chromatography (HPLC) chromatogram on a standard RP-C18 column. It is comparatively higher than that of the other methods examined in this work.

中文翻译：

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通过 SIBX 介导的还原胺化合成和表征光学纯 Gamma-PNA 骨架

手性肽核酸 (PNA) 是常规 PNA 的衍生物，通过在其骨架上引入手性中心，并且已知比常规 PNA 与 DNA 或 RNA 的结合更强。特别是，在 γ-骨架的情况下，L异构体稳定 PNA/DNA 双链，而D-异构体具有相反的作用。因此，合成光学纯的γ-主链是非常重要的。在这里，我们报告了一种新的合成策略，用于在 γ-PNA 主链的合成过程中抑制差向异构化。稳定形式的 2-碘氧基苯甲酸 (SIBX) 在 N-Boc-氨基乙醛合成的关键中间体中用作氧化试剂。本文报道了 (1) 三种不同的 γ-PNA 骨架 (赖氨酸、丙氨酸和谷氨酸) 通过三种不同的合成路线 (SIBX、氢化铝锂和 Red-Al) 的合成和比较和 (2) 手性的测定其衍生化合物的纯度。SIBX 介导的 γ-PNA 骨架的对映体过量纯度被确定为超过 99.4%，由标准 RP-C18 柱上的高效液相色谱 (HPLC) 色谱图确定。它相对高于本工作中检查的其他方法。