Phenylalanine ammonia lyase (PAL) enzymes have been extensively exploited to produce differently substituted arylalanine analogues, but their use in the stereoselective synthesis of aliphatic fatty amino acids has never been addressed. In this work, a two‐step hydroamination‐hydrodesulfurisation process has been investigated for the production of aliphatic L‐α‐amino acids from thienylacrylic acids, easily accessible by condensation from the corresponding arylaldehyde. Wild‐type PALs from Planctomyces brasiliensis and Streptomyces rimosus were selected as the most promising candidates and improved by site‐directed mutagenesis, thus unlocking the hydroamination of a broad panel of 10 different thienylacrylic acids bearing aliphatic and aromatic substituents. The subsequent hydrodesulfurisation step, accomplished by means of inexpensive Raney nickel in mild conditions and aqueous medium, afforded the corresponding aliphatic α‐amino acids in 10‐63% overall isolated yield and perfect enantiopurity. This chemo‐enzymatic process represents the first example of aliphatic amino acid production using PALs, circumventing a major limitation of those biocatalysts.

中文翻译：

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通过化学酶法氢胺化-加氢脱硫法立体选择性合成脂肪族 α-氨基酸


苯丙氨酸解氨酶 （PAL） 已被广泛用于生产不同取代的芳丙氨酸类似物，但它们在脂肪族脂肪酸的立体选择性合成中的应用从未得到解决。在这项工作中，研究了一种两步氢胺化-加氢脱硫工艺，用于从噻吩基丙烯酸生产脂肪族 L-α-氨基酸，很容易通过相应的芳醛缩合获得。来自 Planctomyces brasiliensis 和 Streptomyces rimosus 的野生型 PAL 被选为最有前途的候选者，并通过定点诱变进行改进，从而解锁了 10 种不同噻吩基丙烯酸的广泛组氢胺化，这些丙烯酸含有脂肪族和芳香族取代基。随后的加氢脱硫步骤，通过在温和条件下和水介质中通过廉价的 Raney 镍完成，以 10-63% 的总分离产率和完美的对映体纯度提供了相应的脂肪族 α-氨基酸。这种化学酶促过程代表了使用 PAL 生产脂肪族氨基酸的第一个例子，规避了这些生物催化剂的主要限制。