Institut für Organische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany.
Chembiochem. 2010 Sep 3;11(13):1914-9. doi: 10.1002/cbic.201000296.
2-Methyltetrahydrothiophen-3-one (3) is a volatile compound that plays an important role especially in food and flavour chemistry because it contributes to the aroma of several foodstuffs including wine. Although 3 can be formed by chemical reactions during food preparation, it is also produced by microorganisms. Recent studies with yeasts showed that methionine (1) is a potential precursor of 3, but the mechanism of the transformation is unknown. The biosynthetic pathway leading to 3 in the bacterium Chitinophaga Fx7914 was probed. Extensive feeding experiments with differently labelled precursors by using liquid cultures of Chitinophaga Fx7914 were performed. The volatiles released by the bacterium were collected by using a closed loop stripping apparatus (CLSA) and analysed by GC-MS. The observed incorporation pattern of the precursors into 3 led to the elucidation of the biosynthetic pathway. One part of the compound 2 originates from homocysteine (15), which is transformed into 3-mercaptopropanal (17). The second biosynthetic building block is pyruvate (14). An acyloin-forming reaction furnishes the key intermediate 21, which cyclises intramolecularly to a diol. Dehydration followed by tautomerisation lead to the cyclic ketone 3, which is produced by the bacterium in racemic form.
2-甲基四氢噻吩-3-酮（3）是一种挥发性化合物，它在食品和风味化学中起着重要的作用，因为它有助于几种食品的香气，包括葡萄酒。虽然 3 可以通过食品制备过程中的化学反应形成，但它也是由微生物产生的。最近对酵母的研究表明，蛋氨酸（1）是 3 的潜在前体，但转化的机制尚不清楚。本研究探测了细菌 Chitinophaga Fx7914 中 3 的生物合成途径。通过使用 Chitinophaga Fx7914 的液体培养物进行了广泛的用不同标记前体的喂养实验。使用闭路提取装置（CLSA）收集细菌释放的挥发物，并通过 GC-MS 进行分析。观察到的前体掺入 3 的模式导致了生物合成途径的阐明。化合物 2 的一部分来源于同型半胱氨酸（15），其转化为 3-巯基丙醛（17）。第二个生物合成构建块是丙酮酸（14）。醛缩合反应提供关键中间体 21，其分子内环化形成二醇。脱水后互变异构导致环状酮 3 的形成，细菌以外消旋形式产生 3。
