Isotope labeling studies performed using lysine/glucose model systems have indicated that lysine can generate piperidine, a reactive amine capable of undergoing Maillard type interactions. Two possible mechanisms were identified for the formation of piperidine: one arising through decarboxylation of lysine alone to generate cadaverine (1,5-diaminopentane) followed by deamination to form pent-4-en-1-amine which in turn can cyclize into piperidine where both Nε and Nα atoms of lysine can be equally involved in its generation due to the symmetrical nature of the precursor diamine. On the other hand, in the presence of sugars, lysine, similarly to asparagine and phenylalanine, can undergo carbonyl-assisted decarboxylative deamination reaction to generate pent-4-en-1-amine, the counterpart of acrylamide. The pent-4-en-1-amine can then cyclize to form piperidine through the Nε atom of lysine. To confirm the formation of pent-4-en-1-amine in the lysine/glucose model system, a useful strategy based on Py-GC/MS analysis was developed using isotope labeling technique to identify sugar adducts of pent-4-en-1-amine. Products simultaneously possessing five lysine carbon atoms (C2′−C6′) and the Nε-amino group from lysine in addition to glucose carbon atoms were targeted using specifically labeled precursors such as [¹⁵Nα]lysine·2HCl, [¹⁵Nε]lysine·2HCl, [U-¹³C₆]lysine·2HCl, [¹³C-6]lysine·2HCl and [U-¹³C₆]glucose. The complete labeling studies along with structural analysis using synthetic and other available precursors have shown the presence of a peak that satisfies the above criteria, and the peak was tentatively identified as N-(5-methylfuran-2-yl)methylidene]penta-1,3-dien-1-amine incorporating pent-4-en-1-amine in its structure.

中文翻译：

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Pent-4-en-1-胺的形成，赖氨酸的丙烯酰胺对映体及其在赖氨酸/葡萄糖反应混合物中的转化为哌啶

使用赖氨酸/葡萄糖模型系统进行的同位素标记研究表明，赖氨酸可以产生哌啶，哌啶是一种能够经历美拉德型相互作用的反应性胺。鉴定出了形成哌啶的两种可能机理：一种是仅通过赖氨酸的羧化反应生成尸胺（1,5-二氨基戊烷），然后进行脱氨基反应生成戊-4-烯-1-胺，而后者又可以环化成哌啶。由于前体二胺的对称性质，赖氨酸的Nε和Nα原子均可同等地参与其生成。另一方面，在有糖的情况下，与天冬酰胺和苯丙氨酸相似，赖氨酸可以进行羰基辅助的脱羧脱氨反应，生成与丙烯酰胺对应的戊4-1-1胺。然后，戊-4-烯-1-胺可通过赖氨酸的Nε原子环化形成哌啶。为了确认赖氨酸/葡萄糖模型系统中戊-4-烯-1-胺的形成，使用同位素标记技术开发了一种基于Py-GC / MS分析的有用策略，以鉴定戊-4-烯-的糖加合物1-胺 使用特别标记的前体，例如[[C2'-C6']和赖氨酸的Nε-氨基，除了葡萄糖碳原子外，还同时具有五个赖氨酸碳原子的产物。¹⁵ Nα]赖氨酸·2HCl的，[ ¹⁵ Nε]赖氨酸·2HCl的，[U- ¹³ C ^ ₆ ]赖氨酸·2HCl的，[ ¹³ C-6]赖氨酸·2HCl的和[U- ¹³ C ^ ₆ ]葡萄糖。完整的标记研究以及使用合成的和其他可用的前体进行的结构分析，表明存在满足上述标准的峰，并且该峰暂定为N-（5-甲基呋喃-2-基）亚甲基] penta-1 ，3-dien-1-amine在其结构中并入pent-4-en-1-amine。