Edyta Burda

Enantio‐ and Diastereoselective Chemoenzymatic Synthesis of C2‐Symmetric Biaryl‐Containing Diols

An enantio‐ and diastereoselective synthesis of C2‐symmetric diols bearing a biphenyl‐framework has been developed by means of an enzymatic reduction of the corresponding diketones, which were prepared by a Suzuki coupling reaction. Furthermore, a chemoenzymatic one‐pot synthesis of a C2‐symmetric diol in aqueous media has been realized through combination of the Suzuki coupling reaction and enzymatic reduction. Chiral stereoisomers of the biaryl‐containing diols are prepared with diastereomeric ratios in excess of 25:1 and enantiomeric excesses of greater than 99 %.

Highly conserved progesterone 5β-reductase genes (P5βR) from 5β-cardenolide-free and 5β-cardenolide-producing angiosperms

Most cardenolides used in the therapy of cardiac insufficiency are 5 beta-configured and thus the stereo-specific reduction of the Delta(4,5)-double bond of a steroid precursor is a crucial step in their biosynthesis. This step is thought to be catalysed by progesterone 5 beta-reductases. We report here on the isolation of 11 progesterone 5 beta-reductase (P5 beta R) orthologues from 5 beta-cardenolide-free and 5 beta-cardenolide-producing plant species belonging to five different angiosperm orders (Brassicales, Gentianales, Lamiales, Malvales and Solanales). Amino acid sequences of the P5 beta R described here were highly conserved. They all contain certain motifs qualifying them as members of a class of stereo-selective enone reductases capable of reducing activated C=C double bonds by a 1,4-addition mechanism. Protein modeling revealed seven conserved amino acids in the substrate-binding/catalytic site of these enzymes which are all supposed to exhibit low substrate specificity. Eight P5 beta R genes isolated were expressed in Escherichia coli. Recombinant enzymes reduced progesterone stereo-specifically to 5 beta-pregane-3,20-dione. The progesterone 5 beta-reductases from Digitalis canariensis and Arabidopsis thaliana reduced activated C=C double bonds of molecules much smaller than progesterone. The specific role of progesterone 5 beta-reductases of P5 beta Rs in cardenolide metabolism is challenged because this class of enone reductases is widespread in higher plants, and they accept a wide range of enone substrates.

Highly Enantioselective Reduction of α-Methylated Nitroalkenes†

Highly selective: The reduction of α-methyl-substituted nitroalkenes succeeds in a highly enantioselective fashion with an ene reductase from Gluconobacter oxydans. Under optimized reaction conditions the desired nitroalkanes are formed with enantiomeric excesses of up to 95% in these biotransformations.