Limonene is one of the most abundant naturally occurring cyclic monoterpenes and has recently emerged as a sustainable alternative to petroleum-based solvents as well as a chemical platform for the production of value-added compounds. The biocatalytic epoxidation of both enantiomers of limonene was carried out in the presence of a peroxygenase-containing preparation from oat (Avena sativa) flour. Different reaction profiles were observed depending on the starting enantiomer of limonene, but in both cases the 1,2-monoepoxide was obtained as the main product with excellent diastereoselectivity. Trans-1,2-monoepoxide and cis-1,2-monoepoxide were isolated from the reaction of (R)-limonene and (S)-limonene, respectively, and the reactions were scaled-up to 0.17 M substrate concentration. The process is valuable for operational simplicity, lack of toxic metal catalysts, and cost-effectiveness of the enzymatic source. Pure stereoisomers of 1,2-monoepoxides of limonene constitute a useful starting material for biorenewable polymers, but can be also converted into other chiral derivatives by epoxide ring opening with nucleophiles. As a proof of concept, a tandem protocol for the preparation of enantiopure (1S,2S,4R)-1,2-diol from (R)-limonene and (1R,2R,4S)-1,2-diol from (S)-limonene was developed.

中文翻译：

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燕麦种子过氧化酶催化柠檬烯立体特异性环氧化反应

柠檬烯是最丰富的天然环状单萜之一，最近已成为石油基溶剂的可持续替代品，以及生产增值化合物的化学平台。在来自燕麦（Avena sativa）面粉的含过氧化酶的制剂存在下进行柠檬烯的两种对映异构体的生物催化环氧化。根据柠檬烯的起始对映异构体观察到不同的反应曲线，但在这两种情况下，1,2-单环氧化物均作为主要产物获得，具有优异的非对映选择性。反式-1,2-单环氧化物和顺式-1,2-单环氧化物由( R )-柠檬烯与( S)-柠檬烯，反应放大至 0.17 M 底物浓度。该方法的价值在于操作简单、不含有毒金属催化剂以及酶源的成本效益。柠檬烯的 1,2-单环氧化物的纯立体异构体构成了生物可再生聚合物的有用起始材料，但也可以通过亲核试剂的环氧化物开环转化为其他手性衍生物。作为概念证明，从 ( R )-柠檬烯和 (1 R ,2 R ,4 S )-1制备对映体纯 (1 S ,2 S ,4 R )-1,2-二醇的串联方案，开发了来自 ( S )-柠檬烯的2-二醇。