Although Z-2-oxo-4-methyl-3-pentene-1,5-dioic acid (Z-OMPD) has been identified as a major dicarboxylic acid in tulip tissues, its biosynthetic pathway has not been elucidated. Herein, Z-OMPD was isolated from tulip leaves and chemically synthesized. Comparisons of these samples revealed that Z-OMPD exists as a tautomeric mixture at physiological pH. As a regioisomer of Z-OMPD, we enzymatically and chemically prepared 4-methylene-2-oxo-glutaric acid (4-MEOG) for the first time. Using these compounds as standards, the occurrence of Z-OMPD and 4-MEOG in various tissues of the tulip cultivar "Murasakizuisho" was evaluated directly and by 2,4-dinitrophenylhydrazone derivatization. Z-OMPD was found to be abundant in the aerial tissues, whereas 4-MEOG was almost absent from all tissues. Stability analyses of Z-OMPD and 4-MEOG revealed that no double bond isomerization occurred at physiological pH, suggesting that enzyme systems are responsible for Z-OMPD biosynthesis in tulip tissues.

中文翻译：

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郁金香组织中存在 Z-2-oxo-4-methyl-3-pentene-1,5-dioic acid 及其区域异构体 4-methylene-2-oxo-glutaric acid。

尽管 Z-2-oxo-4-methyl-3-pentene-1,5-dioic acid (Z-OMPD) 已被确定为郁金香组织中的主要二羧酸，但其生物合成途径尚未阐明。在此，Z-OMPD 从郁金香叶中分离出来并化学合成。这些样品的比较表明，Z-OMPD 在生理 pH 值下以互变异构体混合物的形式存在。作为Z-OMPD的区域异构体，我们首次通过酶法和化学方法制备了4-亚甲基-2-氧代-戊二酸（4-MEOG）。以这些化合物为标准，通过2,4-二硝基苯腙衍生化直接评价了郁金香品种“Murasakizuisho”不同组织中Z-OMPD和4-MEOG的发生情况。发现 Z-OMPD 在气生组织中含量丰富，而 4-MEOG 在所有组织中几乎不存在。