Retention stereochemistry in ligand coupling reaction of optically active (1 R)-phenylethyl 2-quinolyl (R)- and (S)-sulfoxide with methylmagnesium bromide

Reactions of (+)-(1R)-phenylethyl 2-quinolyl (R)- sulfoxide 7a and (−)-(1R)-phenylethyl 2-quinolyl (S)- sulfoxide 7b with methylmagnesium bromide were examined. The reaction gave (R)-2-(1-phenylethyl)quinoline 9 as a ligand-coupling product, and a mixture of methyl(1R)-phenylethyl(R)-and (S)-sulfoxide 11a and 11b as ligand exchange products. The other (S) stereoisomer at the 1-phenylethyl carbon center was not detected in the reaction products. That is, both the ligand coupling and ligand exchange reactions proceeded with retention of configuration at the asymmetric carbon center.     

A Compound I Mimic Reveals the Transient Active Species of a Cytochrome P450 Enzyme: Insight into the Stereoselectivity of P450-Catalysed Oxidations

Catching the structure of cytochrome P450 enzymes in flagrante is crucial for the development of P450 biocatalysts, as most structures collected are found trapped in a precatalytic conformation. At the heart of P450 catalysis lies Cpd I, a short-lived, highly reactive intermediate, whose recalcitrant nature has thwarted most attempts at capturing catalytically relevant poses of P450s. We report the crystal structure of P450BM3 mimicking the state in the precise moment preceding epoxidation, which is in perfect agreement with the experimentally observed stereoselectivity. This structure was attained by incorporation of the stable Cpd I mimic oxomolybdenum mesoporphyrin IX into P450BM3 in the presence of styrene. The orientation of styrene to the Mo-oxo species in the crystal structures sheds light onto the dynamics involved in the rotation of styrene to present its vinyl group to Cpd I. This method serves as a powerful tool for predicting and modelling the stereoselectivity of P450 reactions.     

Novel biomaterials derived from deoxyribozyme and NAPzyme

We report the potential of a small Ca²⁺-dependent deoxyribozyme as a novel biomaterial to distinguish RNA foldings. It is found that an immobilized deoxyribozyme using avidin-biotin interaction cleaves the target site within only single-stranded RNAs. The RNA cleavage reaction is also detected using the deoxyribozyme SPR sensor chip. Furthermore, we develop a novel NAPzyme (nucleic acid peptide deoxyribozyme) with its RNA cleavage function in the absence of divalent metal ions.     

Flux-Assisted Synthesis of Y2Ti2O5S2 for Photocatalytic Hydrogen and Oxygen Evolution Reactions

Photocatalytic water splitting is an ideal means of producing hydrogen in a sustainable manner, and developing highly efficient photocatalysts is a vital aspect of realizing this process. The photocatalyst Y₂Ti₂O₅S₂ (YTOS) is capable of absorbing at wavelengths up to 650 nm and exhibits outstanding thermal and chemical durability compared with other oxysulfides. However, the photocatalytic performance of YTOS synthesized using the conventional solid-state reaction (SSR) process is limited owing to the large particle sizes and structural defects associated with this synthetic method. Herein, we report the synthesis of YTOS particles by a flux-assisted technique. The enhanced mass transfer efficiency in the flux significantly reduced the preparation time compared with the SSR method. In addition, the resulting YTOS showed improved photocatalytic H₂ and O₂ evolution activity when loaded with Rh and Co₃O₄ co-catalysts, respectively. These improvements are attributed to the reduced particle size and enhanced crystallinity of the material as well as the slower decay of photogenerated carriers on a nanosecond to sub-microsecond time range. Further optimization of this flux-assisted method together with suitable surface modification is expected to produce high-quality YTOS crystals with superior photocatalytic activity.