[Basic Study on Organic Electron Transfer Reactions by Electrochemistry Combined with Quantum Chemical Calculations]

This review summarizes the results of the author's basic research on organic electrochemistry conducted at Gifu Pharmaceutical University over about 40 years. After completing graduate school, the author became a research associate in Prof. Tanekazu Kubota's laboratory and started research on molecular spectroscopy in 1983. After Prof. Kubota retired in 1989, the author continued investigations in the field of organic electrochemistry as an independent researcher. At that time, a research environment in which ab initio molecular orbital calculations can be used as an analytical tool for experimental research was developed, and the author commenced research on organic electrochemistry combined with quantum chemical calculations as a lifework. The author's research topics were basic research on the molecular theory of redox potentials of organic molecules, molecular design of functional molecules, intermolecular interactions of organic molecules involving electron transfers and electron transfer systems composed of bioactive quinones, and analytical application research based on the basic electrochemistry. In this review article, the essence of the research results is introduced while reflecting on the existing situation at the time of the research. The author concludes the review by expressing gratitude to all colleagues for supporting the research in the author's laboratory.

Dispersion-induced structural preference in the ultrafast dynamics of diphenyl ether

Dispersion interactions are omnipresent in large aromatic systems and influence the dynamics as intermolecular forces. The structural preference induced by dispersion interactions is demonstrated to influence the excited state dynamics of diphenyl ether (DPE) using femtosecond time-resolved transient absorption (TA) associated with quantum chemical calculations. The experimental results in aprotic solvents show that the S₁ state is populated upon irradiation at 267 nm with excess vibrational energy dissipating to solvent molecules in several picoseconds, and then decays via internal conversion (IC) within 50 ps as well as intersystem crossing (ISC) and fluorescence with a lifetime of nanoseconds. The polarity of the solvent disturbs the excited state energies and enhances the energy barriers of the ISC channel. Furthermore, the intermolecular dispersion interactions with protic solvents result in the OH–π isomer dominating in methanol and the OH–O isomer is slightly preferred in t-butanol in the ground state. The hydrogen bonded isomer measurements show an additional change from OH–O to OH–π geometry in the first 1 ps besides the relaxation processes in aprotic solvents. The time constants measured in the TA spectra suggest that the OH–O isomer facilitates IC. The results show that the OH–π isomer has a more rigid structure and a higher barrier for IC, making it harder to reach the geometric conical intersection through conformer rearrangement. This work enables us to have a good knowledge of how the structural preference induced by dispersion interactions affects excited state dynamics of the heteroaromatic compounds.

Dispersion interactions are omnipresent in large aromatic systems and influence the dynamics as intermolecular forces.

Identification of Purines and 7-Deazapurines as Potent and Selective Type I Inhibitors of Troponin I-Interacting Kinase (TNNI3K)

A series of cardiac troponin I-interacting kinase (TNNI3K) inhibitors arising from 3-((9H-purin-6-yl)amino)-N-methyl-benzenesulfonamide (1) is disclosed along with fundamental structure-function relationships that delineate the role of each element of 1 for TNNI3K recognition. An X-ray structure of 1 bound to TNNI3K confirmed its Type I binding mode and is used to rationalize the structure-activity relationship and employed to design potent, selective, and orally bioavailable TNNI3K inhibitors. Identification of the 7-deazapurine heterocycle as a superior template (vs purine) and its elaboration by introduction of C4-benzenesulfonamide and C7- and C8-7-deazapurine substituents produced compounds with substantial improvements in potency (>1000-fold), general kinase selectivity (10-fold improvement), and pharmacokinetic properties (>10-fold increase in poDNAUC). Optimal members of the series have properties suitable for use in in vitro and in vivo experiments aimed at elucidating the role of TNNI3K in cardiac biology and serve as leads for developing novel heart failure medicines.

RhombiminesCyclic Tetraimines of trans-1,2-Diaminocyclohexane Shaped by the Diaryl Ether Structural Motif

[reaction: see text] Rhombimines, chiral macrocyclic tetraimines, are preferentially formed because of the structural bias in the reaction of aromatic ether-linked dialdehydes with enantiomerically pure trans-1,2-diaminocyclohexane.