The piperazine-2,5-dione moiety is a useful scaffold for functionalisation to generate bioactive molecules. Synthetic methods for accessing substituted piperazine-2,5-diones involve cyclising dipeptides or building from the already established core. Utilising the latter method, we have developed procedures to condense a variety of methoxylated benzaldehydes to exclusively form (Z,Z)-(benzylidene)piperazine-2,5-diones 7. This methodology can easily be utilised to form both homo- and heterodimeric substituted piperazine-2,5-diones. Subjecting these compounds to hydrogenation affords two isomers. We detail simple NMR analyses that allow for identification of the cis or trans isomers. These analyses, combined with X-ray crystallography have shown that under the hydrogenation conditions used the cis isomer forms as the major product. The synthetic methodology combined with spectral analysis provides a valuable understanding of piperazine-2,5-dione properties.

中文翻译：

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取代哌嗪-2,5-二酮衍生物的合成与光谱研究

哌嗪-2,5-二酮部分是用于功能化以生成生物活性分子的有用支架。获得取代的哌嗪-2,5-二酮的合成方法涉及环化二肽或从已经建立的核心构建。利用后一种方法，我们开发了缩合各种甲氧基化苯甲醛以专门形成 (Z,Z)-(亚苄基)哌嗪-2,5-二酮 7 的程序。这种方法可以很容易地用于形成同二聚体和异二聚体取代的哌嗪-2,5-二酮。将这些化合物进行氢化得到两种异构体。我们详细介绍了简单的核磁共振分析，可以识别顺式或反式异构体。这些分析与 X 射线晶体学相结合表明，在氢化条件下，使用顺式异构体形式作为主要产物。合成方法与光谱分析相结合，为我们提供了对 2,5-哌嗪二酮性质的宝贵理解。