Fluorescence Spectroscopic Insight into the Supramolecular Interactions in DNA-Based Enantioselective Sulfoxidation

Discovering New G-Quadruplex DNA Catalysts in Enantioselective Sulfoxidation Reaction

The natural human telomeric G-quadruplex (G4) sequence d(GGGTTAGGGTTAGGGTTAGGG) HT21 was extensively utilized as a G4 DNA-based catalytic system for enantioselective reactions. Nine oligonucleotides (ODNs) based on this sequence and containing 8-bromo-2′-deoxyadenosine (A^Br), 8-oxo-2′-deoxyadenosine (A^oxo) or β-L-2′-deoxyadenosine (A^L) at different single loop positions were investigated to evaluate their performances as DNA catalysts in an enantioselective sulfoxidation reaction of thioanisole. The substitution of an adenosine in the loops of HT21 with these modified residues had a negligible impact on the G4 DNA structural features, thermal stability, and catalytic activity, since almost all investigated ODNs were able to form G-quadruplexes strictly resembling that of HT21 and catalyze a full conversion of the thioanisole substrate. More marked effects were obtained in chiral selectivity of G4 DNA metalloenzymes, considering that in most cases the DNA-modified catalysts induced lower enantioselectivities compared to the natural one. However, the HT21 derivative containing an A^L residue in the first loop sequence significantly proved to be capable of producing about 84% enantiomeric excess, the highest enantioselectivity for DNA-based oxidation reaction to date.

The noncovalent dimerization of a G-quadruplex/hemin DNAzyme improves its biocatalytic properties

While many protein enzymes exert their functions through multimerization, which improves both selectivity and activity, this has not yet been demonstrated for other naturally occurring catalysts. Here, we report a multimerization effect applied to catalytic DNAs (or DNAzymes) and demonstrate that the enzymatic efficiency of G-quadruplexes (GQs) in interaction with the hemin cofactor is remarkably enhanced by homodimerization. The resulting non-covalent dimeric GQ-DNAzyme system provides hemin with a structurally defined active site in which both the cofactor (hemin) and the oxidant (H2O2) are activated. This new biocatalytic system efficiently performs peroxidase- and peroxygenase-type biotransformations of a broad range of substrates, thus providing new perspectives for biotechnological application of GQs.

Modern Stereoselective Synthesis of Chiral Sulfinyl Compounds

Chiral sulfinyl compounds, sulfoxides, sulfoximines, sulfinamides, and other derivatives, play an important role in asymmetric synthesis as versatile auxiliaries, ligands, and catalysts. They are also recognized as pharmacophores found in already marketed and well-sold drugs (e.g., esomeprazole) and used in drug design. This review is devoted to the modern methods of preparation of sulfinyl derivatives in enantiopure or enantiomerically enriched form. Selected new approaches leading to racemic products for which the asymmetric variant can be developed in the future are mentioned as well.