The acyltransferase from Mycobacterium smegmatis (MsAcT) complements the well-established acylation activity of hydrolases in organic solvents with its activity to perform acylation reactions (among other reactions) in an aqueous environment. The enzyme’s potential is however limited, due to its poor regio- and stereoselectivity with enantioselectivities (E-values) below 20 for bulky (aromatic) substrates. By applying computer-guided rational design, a library of single variants was designed that allowed conversion of a set of previously challenging substrates with good activity and E-values up to >200. The computational predictions were found to be in agreement with experimental data, which in turn allowed for the generation of even more active and selective double variants. Overall, the produced set of variants provides a toolbox for the enantioselective acylation of challenging alcohols in water, effectively contributing to an alternative to reactions in organic solvents.

The oxidation of allylic alcohols is challenging to perform in a chemo‐ as well as stereo‐selective fashion at the expense of molecular oxygen using conventional chemical protocols. Here, we report the identification of a library of flavin‐dependent oxidases including variants of the berberine bridge enzyme (BBE) analogue from Arabidopsis thaliana (AtBBE15) and the 5‐(hydroxymethyl)furfural oxidase (HMFO) and its variants (V465T, V465S, V465T/W466H and V367R/W466F) for the enantioselective oxidation of sec‐allylic alcohols. While primary and benzylic alcohols as well as certain sugars are well known to be transformed by flavin‐dependent oxidases, sec‐allylic alcohols have not been studied yet except in a single report. The model substrates investigated were oxidized enantioselectively in a kinetic resolution with an E‐value of up to >200. For instance HMFO V465S/T oxidized the (S)‐enantiomer of (E)‐oct‐3‐en‐2‐ol (1 a) and (E)‐4‐phenylbut‐3‐en‐2‐ol with E>200 giving the remaining (R)‐alcohol with ee>99% at 50% conversion. The enantioselectivity could be decreased if required by medium engineering by the addition of cosolvents (e. g. dimethyl sulfoxide).

Synthesis of Homochiral N-Boc-β-Aminoaldehydes from N-Boc-βaminonitriles.-Enantiopure N-Boc-β-aminoaldehydes (II) are efficiently prepared in good yields by partial reduction of the nitrile function in optically pure N-Boc-β-aminonitriles (I) with diisobutylaluminum hydride. -(TOU-JAS, J.-L.; JOST, E.; VAULTIER, M.; Bull.