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NMR-based investigations of acyl-functionalized piperazines concerning their conformational behavior in solution

机译：基于NMR的酰基官能化哌嗪关于它们在溶液中的构象行为的研究

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摘要

Selected N-benzoylated piperazine compounds were synthesized to study their conformational behavior using temperature-dependent H-1 NMR spectroscopy. All investigated piperazines occur as conformers at room temperature resulting from the restricted rotation of the partial amide double bond. In the case of selected mono-N-benzoylated and unsymmetrically N,N-substituted derivatives, the appearance of the H-1 NMR spectrum was further shaped by the limited interconversion of the piperazine chair conformations. Therefore, two different coalescence points T-C were determined and their resulting activation energy barriers G(double dagger) were calculated to be between 56 and 80 kJ mol(-1). In most of the cases, T-C and G(double dagger) for the amide site appeared to be higher than the corresponding values for the ring inversion. The influences of substituents on rotational and inversion barriers were analyzed by correlation to Hammett constants. The obtained results are discussed and interpreted in the context of literature data. An additional aryl substituent connected at the amine site led to reduced rotational and inversion barriers compared to the free secondary amine. To support and evidence the findings from the NMR analyses, single crystals of selected piperazines were obtained and XRD analyses were performed. To underline the results, two potential TGase 2 inhibitors were investigated showing energy barriers with similar values.
机译：合成所选的N-苯氧化哌嗪化合物以使用温度依赖的H-1 NMR光谱研究它们的构象行为。所有所研究的哌嗪在室温下发生均匀，由部分酰胺双键的受限旋转产生。在选定的单壬-N-苯甲酰化和未对称的N，N-取代的衍生物的情况下，通过哌嗪椅兼容的有限互连进一步成形H-1 NMR光谱的外观。因此，确定了两种不同的聚结点T-C，并计算它们所得的活化能屏障G（双匕首）在56和80kJ摩尔（-1）之间。在大多数情况下，酰胺位点的T-C和G（双匕首）似乎高于环反转的相应值。通过与Hammett常数的相关性分析取代基对旋转和反转屏障的影响。在文献数据的背景下讨论并解释了所获得的结果。与游离仲胺相比，在胺位点连接的另外的芳基取代基导致旋转和反转屏障减少。为了支持和证据来自NMR分析的发现，获得了所选哌嗪的单晶并进行XRD分析。为了强调结果，研究了两个潜在的TGase 2抑制剂，显示出具有相似值的能量屏障。

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  • 来源
    《RSC Advances》 |2018年第71期|共13页
  • 作者

    Wodtke Robert; Steinberg Janine; Koeckerling Martin; Loeser Reik; Mamat Constantin;

  • 作者单位

    Helmholtz Zentrum Dresden Rossendorf Inst Radiopharmazeut Krebsforsch Bautzner Landstr 400 D-01328 Dresden Germany;

    Helmholtz Zentrum Dresden Rossendorf Inst Radiopharmazeut Krebsforsch Bautzner Landstr 400 D-01328 Dresden Germany;

    Univ Rostock Inst Chem Anorgan Anorgan Festkorperchem Albert Einstein Str 4a D-18059 Rostock Germany;

    Helmholtz Zentrum Dresden Rossendorf Inst Radiopharmazeut Krebsforsch Bautzner Landstr 400 D-01328 Dresden Germany;

    Helmholtz Zentrum Dresden Rossendorf Inst Radiopharmazeut Krebsforsch Bautzner Landstr 400 D-01328 Dresden Germany;

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  • 正文语种 eng
  • 中图分类 化学;
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