Biomembranes composed of various proteins and lipids play important roles in cellular functions, such as signal transduction and substance transport. In addition, some bioactive peptides and pathogenic proteins target membrane proteins and lipids to exert their effects. Therefore, an understanding of dynamic and complex intermolecular interactions among these membrane constituents is needed to elucidate their mechanisms. This review summarizes the major research carried out in the author’s laboratory on how lipids and their inhomogeneous distributions regulate the structures and functions of antimicrobial peptides and Alzheimer’s amyloid β-protein. Also, how to detect transmembrane helix–helix and membrane protein–protein interactions and how they are modulated by lipids are discussed.

Osmium is defined in the international council for harmonization (ICH-Q3D) guidelines as an element whose concentration can be determined by validated methods including microwave-assisted nitric acid digestion and inductively coupled plasma mass spectrometry. However, microwave digestion using nitric acid is known to result in osmium recoveries higher than the theoretical values in spiked tests because of the formation of highly volatile osmium tetroxide in an oxidation reaction. To stabilize osmium, the addition of thiourea as a complexing agent has been tested and proved its utility. It remains unclear whether other compounds can prevent the over-recovery of osmium. In this study, we investigated four compounds, thiourea, ascorbic acid, sodium sulfite, and potassium metabisulfite, that could reduce the overestimation of osmium isotopes. The minimum amounts of thiourea, ascorbic acid, sodium sulfite, and potassium metabisulfite required to stabilize 10 ng/mL osmium in blank matrix were 1.0, 1.0, 2.5, and 2.5 g/L, respectively. The relative standard deviations obtained from 12 analyses for each stabilization solution were less than 3.3% in thiourea, 12.7% in ascorbic acid, 9.0% in sodium sulfite, and 10.6% in potassium metabisulfite. The stabilization solutions were investigated in a digested tablet matrix and were found to be effective. The impact of adding stabilization solutions on the determination of all ICH-Q3D element concentrations was also evaluated. As stabilization solutions had a small or significant impact on the determination of some elements, it was concluded that osmium determination should be conducted independently.

Soft sensors are powerful tools for the implementation of process analytical technology (PAT). They are categorized into white-box (first-principle), black-box (statistical), and gray-box models. Gray-box models integrate white-box and black-box models to address each drawback, i.e., prediction accuracy and intuitiveness. Although they have been applied to various industrial processes, their applicability to water content monitoring in fluidized bed granulation has not been reported. In this study, we evaluated three types of gray-box models, i.e., parallel, serial, and combined gray-box models, in terms of prediction accuracy using real operating data on a commercial scale with two formulations. The gray-box models were constructed by integrating the heat and mass balance model (white-box model) and locally weighted partial least squares regression (LW-PLSR) model (black-box model). LW-PLSR was utilized to cope with collinearity and nonlinearity. In the serial gray-box models, LW-PLSR models adjusted the fitting parameters of the white-box model depending on the process parameters for each query. In the parallel gray-box or combined gray-box models, LW-PLSR models compensated for the output error of the white-box or serial gray-box models, respectively. The results demonstrated that all three types of gray-box models improved the prediction accuracy of the white-box models regardless of the formulation. Besides, we proposed the assessment method based on Hotelling’s T² and Q residual for gray-box models using LW-PLSR, which contributes decision support to select gray-box or white-box model. The accurate and descriptive gray-box models are expected to enhance process understanding and precise quality control in fluidized bed granulation.

Considerable efforts have been made on the development of lipid nanoparticles (LNPs) for delivering of nucleic acids in LNP-based medicines, including a first-ever short interfering RNA (siRNA) medicine, Onpattro, and the mRNA vaccines against the coronavirus disease 2019 (COVID-19), which have been approved and are currently in use worldwide. The successful rational design of ionizable cationic lipids was a major breakthrough that dramatically increased delivery efficiency in this field. The LNPs would be expected to be useful as a platform technology for the delivery of various therapeutic modalities for genome editing and even for undiscovered therapeutic mechanisms. In this review, the current progress of my research, including the molecular design of pH-sensitive cationic lipids, their applications for various tissues and cell types, and for delivering various macromolecules, including siRNA, antisense oligonucleotide, mRNA, and the clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) system will be described. Mechanistic studies regarding relationships between the physicochemical properties of LNPs, drug delivery, and biosafety are also summarized. Furthermore, current issues that need to be addressed for next generation drug delivery systems are discussed.

Isoxazolidin-5-ones have been regarded as β-amino acid surrogates owing to their labile N–O bond. While many efforts have been devoted to the catalytic enantioselective synthesis of the core of this heterocycle, its further transformation has been less explored, especially in the context of catalysis. This review summarizes the author’s research on the development of catalytic reactions using isoxazolidin-5-ones as substrates. Asymmetric catalysis has proven effective for C–C bond formation at the carbonyl α-carbon. Catalytic asymmetric allylation and direct Mannich-type reactions have been developed. Further, the resulting products have been readily converted into the corresponding quaternary β^2,2-amino acids. Moreover, isoxazolidin-5-ones have been identified as alkyl nitrene precursors in the presence of a suitable metal catalyst. The generated metallonitrene undergoes either the electrophilic amination of the aromatic ring or aliphatic C–H insertion, affording a series of cyclic β-amino acids. A remarkable difference in chemoselectivity between rhodium and copper alkyl nitrenes has also been demonstrated, highlighting the unique nature of the underexplored reactive intermediates. The various linear and cyclic β-amino acids obtained through the study are likely to find great utility in a broad range of chemical sciences.

The ability to control the reactions of highly active chemical species to enable straightforward synthesis of valuable compounds such as bioactive natural products and pharmaceuticals is a continuing challenge in synthetic organic chemistry. This review describes the development of a methodology using reactive metal-carbene species and its synthetic application in our laboratory. First, regioselective synthesis of γ-amino acid equivalents to take advantage of their metal-dependent reactivities and the mechanistic rationale are presented. Chemoselective and enantioselective dearomatization reactions of several arenes with silver-carbene are also discussed. In the second half of the review, we discuss a carbene-insertion reaction into an amide and urea C–N bond for the assembly of nitrogen-bridged cyclic molecules.

A series of quinone derivatives with a variety of side chains were synthesized. These synthetic quinone compounds were evaluated for in vitro antitrypanosomal activity against trypomastigotes and amastigotes of Trypanosoma cruzi, the causative agent of Chagas disease. Measurement of solubility of quinones and their ability to permeate cell membranes were assessed to address their possible use as oral drugs. Some synthesized compounds exhibited potent antitrypanosomal activity. However, most compounds with a promising activity showed poor solubility that did not seem suitable for oral usage. Meanwhile, compound 5a, an N-tert-butoxycarbonylpiperidine derivative, exhibited good antitrypanosomal activity, ability to permeate membranes, and good solubility.

Extracellular vesicles (EVs) have emerged as important targets in biological and medical studies because they are involved in diverse human diseases and bacterial pathogenesis. Although antibodies targeting the surface biomarkers are widely used to detect EVs, peptide-based curvature sensors are currently attracting an attention as a novel tool for marker-free EV detection techniques. We have previously created a curvature-sensing peptide, FAAV and applied it to develop a simple and rapid method for detection of bacterial EVs in cultured media. The method utilized the fluorescence/Förster resonance energy transfer (FRET) phenomenon to achieve the high sensitivity to changes in the EV amount. In the present study, to develop a practical and easy-to-use approach that can detect bacterial EVs by peptides alone, we designed novel curvature-sensing peptides, N-terminus-substituted FAAV (nFAAV) peptides. The nFAAV peptides exerted higher α-helix-stabilizing effects than FAAV upon binding to vesicles while maintaining a random coil structure in aqueous solution. One of the nFAAV peptides showed a superior binding affinity for bacterial EVs and detected changes in the EV amount with 5-fold higher sensitivity than FAAV even in the presence of the EV-secretory bacterial cells. We named nFAAV5, which exhibited the high ability to detect bacterial EVs, as an EV-sensing peptide. Our finding is that the coil–α-helix structural transition of the nFAAV peptides serve as a key structural factor for highly sensitive detection of bacterial EVs.

From the viewpoint of self-medication, it is valuable to develop patient-friendly scored tablets that possess dividing uniformity. In this context, we attempted to optimize the preparation conditions for a tablet with a unique shape, such as a concavely curved scored tablet (CCST). Employing a design of experiment and a response surface method incorporating a thin-plate spline interpolation, and a bootstrap resampling technique, the optimal preparation conditions for CCST were successfully developed. To make it possible to scaleup the optimal solution estimated on a trial-scale, a Bayesian estimation was applied. Credible ranges of critical responses in large-scale manufacturing were estimated as a posterior probability from the trial-scale experiment as a prior probability. In terms of the large-scale manufacturing, the possibility of solving the scaleup problem was suggested using Bayesian estimation. Furthermore, a simulation study using a finite element method revealed that strong tensile stresses generated along the tip of the score line in CCST when an outer force was applied to the back surface of CCST. An advantage in dividing uniformity is indicated by the unique shape of CCST.

In this study, a series of alkyl diamine linked bivalent β-carbolines was synthesized and evaluated as antitumor agent. The results demonstrated that most compounds displayed good antiproliferative activities with IC₅₀ value lower than 10 µM against a panel of human tumor cell lines, and compound 8 was found to be the most potent antiproliferative agent with IC₅₀ value of 1.39, 1.96, 1.42, 1.49, 1.32, 1.96 and 1.63 µM against human breast cancer cell line (MCF-7), human adenocarcinoma cell line (769-P), human malighant melanoma cell line (A375), human ovarian cancer cell line (SK-OV-3), human colon carcinoma cell line (HCT-116), human gastric cancer cell line (BGC-823) and human esophageal squamous carcinoma cell line (Eca-109), respectively. Further investigations on mechanism of action of this class of compound demonstrated that the representative compound 8 inhibited colorectal cancer growth through inducing autophagy.

Nicotinamide phosphoribosyltransferase (NAMPT) catalyzes the rate-limiting step of the nicotinamide adenine dinucleotide (NAD⁺) salvage pathway. Because NAD⁺ plays a pivotal role in energy metabolism and boosting NAD⁺ has positive effects on metabolic regulation, activation of NAMPT is an attractive therapeutic approach for the treatment of various diseases, including type 2 diabetes and obesity. Herein we report the discovery of 1-(2-phenyl-1,3-benzoxazol-6-yl)-3-(pyridin-4-ylmethyl)urea 12c (DS68702229), which was identified as a potent NAMPT activator. Compound 12c activated NAMPT, increased cellular NAD⁺ levels, and exhibited an excellent pharmacokinetic profile in mice after oral administration. Oral administration of compound 12c to high-fat diet-induced obese mice decreased body weight. These observations indicate that compound 12c is a promising anti-obesity drug candidate.

Control of site selectivity is an exciting direction for synthetic organic chemistry owing to the possibility of selective modification of multifunctionalized molecules, ultimately including biomacromolecules. In this review, our recent research related to site selectivity in two types of transformation, namely, the acylation of hydroxy groups and C–H amination, is summarized. Regarding the acylation of hydroxy groups, catalyst-controlled site selectivity enables unconventional retrosynthetic analysis, leading to efficient syntheses of sugar-related natural and unnatural products. Regarding C–H amination, the discovery of unprecedented reaction sites in intermolecular amination mediated by dirhodium nitrenes is described. The findings of this research demonstrate the power of site-selective transformation in the synthesis of a particular class of compounds.

Nitroxyl radicals, such as 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO), can catalyze the electrochemical oxidation of alcohols and amines. Because the oxidation current obtained in this process depends on the concentration of alcohols and amines, this process can be applied to their sensing. However, the relatively high oxidation potentials required by nitroxyl radicals can induce interfering oxidation currents from various reductive substances in biological samples, which affects the accuracy of analyte measurements. In this study, we examined the electrooxidation of alcohols and amines at a low potential by applying cooperative oxidation catalysis using a nitroxyl radical and a copper salt. Nortropine N-oxyl (NNO), which showed higher catalytic activity than TEMPO was used as the nitroxyl radical. An increase in the oxidation current was observed at the low potential, and this increase depended on the alcohol concentration. In the case of the electrooxidation of amines, a positive correlation between oxidation current and amine concentration was observed at low amine concentrations. Therefore, low-potential cooperative catalysis can be applied to alcohol and amine electrooxidation for the development of accurate sensors suitable for clinical settings.

α,β-Unsaturated oximes underwent electrophilic epoxidation with in-situ-generated dimethyldioxirane to give the corresponding epoxides in good yields. This reaction is an example of “carbonyl umpolung” by transformation of α,β-unsaturated ketones to their oximes. Nucleophilic ring-opening reactions of the epoxides afforded α-substituted products. Shi asymmetric epoxidation of the oximes proceeded with moderate enantioselectivity.

Spiroviolene is a spirocyclic triquinane diterpene produced by Streptomyces violens. Recently, a biosynthetic pathway that includes secondary carbocation intermediates and a complicated concerted skeletal rearrangement was proposed for spiroviolene, based upon careful labeling experiments. On the basis of density functional theory (DFT) calculations, we propose a revised pathway for spiroviolene biosynthesis, involving a multistep carbocation cascade that bypasses the formation of unstable secondary carbocations by breaking the adjacent C–C bond to form a more stable tertiary carbocation (IM3) and by Wagner–Meerwein 1,2-methyl rearrangement (IM7).

Novel innovative catalytic systems such as hydrogen-bond donors and thiourea hybrid catalysts have been developed for the asymmetric synthesis of biologically important pharmaceuticals and natural products. Benzothiadiazines possess a stronger hydrogen-bond donor ability compared to thioureas and exhibit remarkable catalytic performance for the activation of α,β-unsaturated amides. Hybrid thioureas (bearing an arylboronic acid and an ammonium salt) efficiently promote the hetero-Michael addition to α,β-unsaturated carboxylic acids and the O-alkylation of keto enols with 5-chlorofuran-2(5H)-one. These hybrid catalysts enable the first total synthesis of non-racemic avenaol, a noncanonical strigolactone, as well as the asymmetric synthesis of several pharmaceuticals. In addition, this study discovers unique chemical phenomena (i.e., the dual role of benzoic acid as a boron ligand and a proton shuttle, the chirality switch of products by solvent used, and the dynamic kinetic resolution of a racemic electrophile in an S_N2-type reaction).

Active pharmaceutical ingredients (APIs) have become a public concern owing to their possible adverse effects on aquatic organisms. Ministry of Health, Labor and Welfare in Japan (MHLW) issued “Guidance on the Environmental Risk Assessment (ERA) in new pharmaceutical development” in 2016. To evaluate the validity of phase 1 in the MHLW’s ERA guidance, we monitored the measured environmental concentrations (MECs) of approved APIs in urban rivers and sewage treatment plants (STPs) in Japan and compared these MECs with the predicted environmental concentration (PEC). We collected water samples from urban seven rivers and three STPs during each season. Fifty-one APIs for human and veterinary use and the artificial sweetener sucralose were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Forty-four APIs were observed in the rivers and 42 were found in the influent and effluent of STPs, with levels ranging from nanograms to micrograms per liter. The action limit in phase I of the MHLW’s guidance was set to 10 ng/L, and there was no API except for ketoprofen, for which PEC of the MHLW’s guidance (PECjapan) was lower than 10 ng/L and the maximum MEC (MECmax) was 10 ng/L or greater. Almost all APIs also had median MECs that were lower than those of the respective PECjapan. These results indicate that the PECjapan values in phase I of the MHLW’s guidance were appropriate. However, some APIs had MECmax values that were greater than those of the respective PECjapan due to overestimation of the dilution factor of river water and/or underestimation of API production.

Proviral integration site for Moloney murine leukemia virus (PIM) kinases are proto-oncogenic kinases involved in the regulation of several cellular processes. PIM kinases are promising targets for new drug development because they play a major role in many cancer-specific pathways, such as survival, apoptosis, proliferation, cell cycle regulation, and migration. Here, 2-thioxothiazolidin-4-one derivatives were synthesized and evaluated as potent pan-PIM kinase inhibitors. Optimized compounds showed single-digit nanomolar IC₅₀ values against all three PIM kinases with high selectivity over 14 other kinases. Compound 17 inhibited the growth of Molm-16 cell lines (EC₅₀ = 14 nM) and modulated the expression of pBAD and p4EBP1 in a dose-dependent manner.