Dario A. Bianchi

Accessing tetrahydrofuran-based natural products by microbial Baeyer–Villiger biooxidation

A heterobicyclic lactone obtained by stereoselective Baeyer-Villiger biooxidation with recombinant whole-cells expressing cyclopentanone monooxygenase from Comamonas sp. NCIMB 9872 was used for formal total syntheses of various natural products containing a tetrahydrofuran structural motif.

Flavoprotein monooxygenases for oxidative biocatalysis: recombinant expression in microbial hosts and applications

External flavoprotein monooxygenases comprise a group of flavin-dependent oxidoreductases that catalyze the insertion of one atom of molecular oxygen into an organic substrate and the second atom is reduced to water. These enzymes are involved in a great number of metabolic pathways both in prokaryotes and eukaryotes. Flavoprotein monooxygenases have attracted the attention of researchers for several decades and the advent of recombinant DNA technology caused a great progress in the field. These enzymes are subjected to detailed biochemical and structural characterization and some of them are also regarded as appealing oxidative biocatalysts for the production of fine chemicals and valuable intermediates toward active pharmaceutical ingredients due to their high chemo-, stereo-, and regioselectivity. Here, we review the most representative reactions catalyzed both in vivo and in vitro by prototype flavoprotein monooxygenases, highlighting the strategies employed to produce them recombinantly, to enhance the yield of soluble proteins, and to improve cofactor regeneration in order to obtain versatile biocatalysts. Although we describe the most outstanding features of flavoprotein monooxygenases, we mainly focus on enzymes that were cloned, expressed and used for biocatalysis during the last years.

Enantiocomplementary access to carba-analogs of C-nucleoside derivatives by recombinant Baeyer–Villiger monooxygenases

A novel and stereoselective synthetic route towards carba-C-nucleosides was investigated applying an enantiodivergent biooxidation strategy by two different Baeyer-Villiger monooxygenases. Within only three chemo-enzymatic steps it was possible to introduce four chiral centers starting from commercially available non-chiral starting material.

Polysubstituted Isochroman Derivatives with Plant Growth Regulating Properties on Wheat (Triticum aestivum L. cv Klein Escorpion)

The synthesis of isochroman derivatives 4–9 from α-hydroxylactone 3 is reported. These heterocycles, carrying different substituents on C-3, C-4, and C-8, exhibited different degrees of inhibition of the vegetative growth of wheat (Triticum aestivum cv Klein Escorpion) plants, whereas plant developmental patterns such as their protein profile, carotenes/chlorophylls ratio, and weight/length relationship were not significantly affected. Microscopic observation of transverse sections of shoots and roots showed morphological changes in the treated plants, consistent with delayed development. The results suggest that among these isochromans the C-3 carbonyl moiety of the lactone and the C-4 free hydroxyl group are important but not essential for activity, and that a short side chain appended to C-3 is tolerated. However, cleavage of the C-8 methyl ether group to the related free phenol causes a drastic reduction in the growth inhibitory activity.

Carbonyl transposition of α-hydroxyamidals mediated by triphenylphosphine-iodine. A new entry to tetrahydroisoquinolin-4-ones

Abstract Carbonyl transposition of 2-sulfonyl-3-methoxy-4-hydroxy-tetrahydroisoquinolines with the triphenylphosphine-iodine reagent provides a new access to tetrahydroisoquinolin-4-one derivatives.

Cloning and characterization of the Type I Baeyer–Villiger monooxygenase from Leptospira biflexa

Baeyer–Villiger monooxygenases are recognized by their ability and high selectivity as oxidative biocatalysts for the generation of esters or lactones using ketones as starting materials. These enzymes represent valuable tools for biooxidative syntheses since they can catalyze reactions that otherwise involve strong oxidative reagents. In this work, we present a novel enzyme, the Type I Baeyer–Villiger monooxygenase from Leptospira biflexa. This protein is phylogenetically distant from other well-characterized BVMOs. In order to study this new enzyme, we cloned its gene, expressed it in Escherichia coli and characterized the substrate scope of the Baeyer–Villiger monooxygenase from L. biflexa as a whole-cell biocatalyst. For this purpose, we performed the screening of a collection of ketones with variable structures and sizes, namely acyclic ketones, aromatic ketones, cyclic ketones, and fused ketones. As a result, we observed that this biocatalyst readily oxidized linear- and branched- medium-chain ketones, alkyl levulinates and linear ketones with aromatic substituents with excellent regioselectivity. In addition, this enzyme catalyzed the oxidation of 2-substituted cycloketone derivatives but showed an unusual selection against substituents in positions 3 or 4 of the ring.