Optically pure lactams have a wide diversity of applications, one of which is serving as important intermediates in the synthesis of agricultural bioactive compounds or pharmaceuticals. Efficient stereoselective synthesis of chiral lactams with low-cost amine donors under mild conditions is desired for manufacturing of these important chemicals. Herein, a two-step chemo-enzymatic strategy has been designed to produce (S)-lactams by engineering a natural amine dehydrogenase from Thermoanaerobacter thermohydrosulfuricus (TtherAmDH). TtherAmDH was subjected to eight cycles of directed evolution to enhance its reductive amination activity toward keto acid substrates. The variants showed improved specific activity toward 6 tested substrates and gave high stereoselectivities of up to 99% in the asymmetric synthesis of γ- and δ- lactams. In particular, TtherAmDH_V8 showed a 237-fold higher specific activity toward the model substrate levulinic acid and gave (S)-5-methyl-2-pyrrolidone in 99% ee with a space-time yield of 75.3 g L⁻¹ d⁻¹. These results indicate that the engineered amine dehydrogenase TtherAmDH can serve as an efficient biocatalyst for the manufacture of highly valued chiral lactams.

中文翻译：

---

通过工程胺脱氢酶立体选择性合成结构多样 (S)-内酰胺

光学纯内酰胺具有广泛的应用，其中之一是作为合成农业生物活性化合物或药物的重要中间体。制造这些重要化学品需要在温和条件下用低成本胺供体高效立体选择性合成手性内酰胺。在此，设计了一种两步化学酶促策略，通过改造来自Thermoanaerobacter thermohydrosulfuricus ( Tther AmDH)的天然胺脱氢酶来生产 ( S )-内酰胺。其他AmDH 经过八个定向进化循环，以增强其对酮酸底物的还原胺化活性。这些变体对 6 种测试底物显示出更高的比活性，并在 γ- 和 δ- 内酰胺的不对称合成中提供高达 99% 的高立体选择性。特别是，Tther AmDH _V8对模型底物乙酰丙酸表现出高 237 倍的比活性，并产生 99% ee的 ( S )-5-甲基-2-吡咯烷酮，时空产率为 75.3 g L ^-1  d ^-1。这些结果表明，工程化的胺脱氢酶Tther AmDH 可以作为一种有效的生物催化剂，用于制造高价值的手性内酰胺。