The continuous flow synthesis of a series of amines was successfully achieved by exploiting the enhanced stability and broad substrate scope of an immobilised transaminase from Halomonas elongata (HEWT).

Chiral amines are indispensable building blocks in the production of biologically active compounds. They are fundamental for the pharmaceutical industry, both as active molecules themselves and as chiral auxiliaries in asymmetric synthesis; however, the available synthetic strategies often present disadvantages. ω-Transaminases (ω-TAs) appear as an attractive alternative by driving the stereoselective amination of prochiral ketones. HEWT is a novel amine transaminase from the moderate halophilic bacterium, Halomonas elongata DSM 2581, which is highly (S)-selective, being able to fully convert (S)-1-phenylethylamine to acetophenone and showing no activity with the corresponding (R)-1-phenylethylamine. HEWT has a broad substrate scope, active with a range of amino donors and acceptors, and naturally accepts isopropylamine (IPA) as amino donor in asymmetric synthesis providing a 41% conversion of pyruvate in 24 h at 37 °C starting with 1:1 molar ratio between the reagents. HEWT also accepts ortho-xylylenediamine as amino donor in for amine synthesis, in particular, with benzaldehyde yielding high conversions between 90 and 95%. The enzyme is also tolerant to the presence of cosolvents up to 20% making it a promising candidate for industrial applications

Directed evolution of transaminases is a widespread technique in the development of highly sought-after biocatalysts for industrial applications.

A new transaminase (VbTA) was identified from the genome of the halotolerant marine bacterium Virgibacillus 21D. Following heterologous expression in Escherichia coli, it was located entirely in the insoluble fraction. After a single mutation, identified via sequence homology analyses, the VbTA T16F mutant was successfully expressed in soluble form and characterised. VbTA T16F showed high stability towards polar organic solvents and salt exposure, accepting mainly hydrophobic aromatic amine and carbonyl substrates. The 2.0 Å resolution crystal structure of VbTA T16F is here reported, and together with computational calculations, revealed that this mutation is crucial for correct dimerisation and thus correct folding, leading to soluble protein expression.

In the light of the promising bioactivity of the tetraarsenic marine metabolite arsenicin A, the dimethyl analogue 2 and four isomeric methylene homologues (including the natural product itself) were obtained using a one-pot microwave-assisted synthesis, starting from arsenic (III) oxide. Due to the poor diagnostic value of the NMR technique in the structural elucidation of these molecules, they were fully characterized by mass spectrometry and infrared (IR)-spectroscopy, comparing density functional theory (DFT) simulated and experimental spectra. This synthetic procedure provided a fast and efficient access to the cytotoxicity evaluation of organoarsenical leads of the natural hit molecule. From in vitro screening, each tested compound resulted in being more active than the FDA-approved arsenic trioxide, with the most lipophilic molecule in the series showing the best growth inhibition of both leukemia and solid tumor cell lines. These results may open promising perspectives in the development of new more potent and selective arsenical drugs against solid tumors.