Three neo-clerodane diterpenoids, including two new tinocordifoliols A (1) and B (2) and one known tinopanoid R (3), were isolated from the ethyl acetate-soluble fraction of the 70% ethanol extract of Tinospora cordifolia stems. The structures were elucidated by various spectroscopic methods, including one dimensional (1D) and 2D-NMR, high resolution-electrospray ionization (HR-ESI)-MS, and electronic circular dichroism (ECD) data. The T. cordifolia extract and all isolated compounds 1–3 possessed arginase I inhibitory activities. Among them, 3 exhibited moderate competitive inhibition of human arginase I (IC₅₀ = 61.9 µM). Furthermore, docking studies revealed that the presence of a β-substituted furan in 3 may play a key role in the arginase I inhibitory activities.

Dihydrobenzofuran is an important skeleton for bioactive compounds and natural products. Hydroquinones can be easily modified into substituted hydroquinones, which effectively undergo oxidation to produce the corresponding benzoquinone derivatives. Benzoquinones are reactive electrophiles that are frequently utilized in coupling with olefins to dihydrobenzofurans. Herein, we report the one-pot oxidative coupling of hydroquinones bearing an electron-withdrawing group at the C2 position with olefins to dihydrobenzofurans in the presence of the Lewis acidic FeCl₃ and 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) oxidant. Furthermore, this method was applied to the oxidative coupling of N-electron-withdrawing group-substituted 4-aminophenol.

We report the first total synthesis of silybin A (1). Key synthetic steps include the construction of the 1,4-benzodioxane neolignan skeleton, a modified Julia–Kocienski olefination reaction between m-nitrophenyltetrazole sulfone (m-NPT sulfone) 10 and aldehyde 21, the formation of the flavanol lignan skeleton 28 via a quinomethide intermediate under acidic conditions, and stepwise oxidation of the benzylic position of flavanol 29.

Natural products are important for the development of pharmaceuticals and agrochemicals; thus, their synthesis and medicinal chemistry research is critical. Developing a total synthesis pathway for natural products confirms their structure and provides the opportunity to modify the structure in a targeted manner. A simple modification of a single oxidation step can increase the biological activity, or the complexity of the molecule can alter the property. Herein, we discuss the asymmetric total synthesis of dihydroisocoumarin-type natural products, the creation of novel antibacterial compounds through partial structural modification, and the development of antioxidants with high activity and low toxicity through dimerization strategies.

We have developed efficient synthetic reactions using enamines and enamides carrying oxygen atom substituent on nitrogen, such as N-alkoxyenamines, N,α-dialkoxyenamines, N-alkoxyanamides, and N-(benzoyloxy)enamides. The umpolung reaction by polarity inversion at the β-position of N-alkoxyenamines afforded α-alkyl-, α-aryl-, α-alkenyl-, and α-heteroarylketones by using aluminum reagent as nucleophiles. Furthermore, one-pot umpolung α-phenylation of ketones has been also developed. We applied this method to umpolung reaction of N,α-dialkoxyenamine, generated from N-alkoxyamide to afford α-arylamides. The vicinal functionalization of N-alkoxyenamines has been achieved with the formation of two new carbon–carbon bonds by using an organo-aluminum reagent and subsequent allyl magnesium bromide or tributyltin cyanide. A sequential retro-ene arylation has been developed for the conversion of N-alkoxyenamides to the corresponding tert-alkylamines. The [3,3]-sigmatropic rearrangement of N-(benzoyloxy)enamides followed by arylation afforded cyclic β-aryl-β-amino alcohols bearing a tetrasubstituted carbon center. The resulting products were converted into the corresponding sterically congested cyclic β-amino alcohols, as well as the dissociative anesthetic agent Tiletamine.

The solid-state properties of drug candidates play a crucial role in their selection. Quality control of active pharmaceutical ingredients (APIs) based on their structural information involves ensuring a consistent crystal form and controlling water and residual solvent contents. However, traditional crystallographic techniques have limitations and require high-quality single crystals for structural analysis. Microcrystal electron diffraction (microED) overcomes these challenges by analyzing difficult-to-crystallize or small-quantity samples, making it valuable for efficient drug development. In this study, microED analysis was able to rapidly determine the configuration of two crystal forms (Forms 1, 2) of the API ranitidine hydrochloride. The structures obtained with microED are consistent with previous structures determined by X-ray diffraction, indicating microED is a useful tool for rapidly analyzing molecular structures in drug development and materials science research.

Heterologous expression of natural compound biosynthetic gene clusters (BGCs) is a robust approach for not only revealing the biosynthetic mechanisms leading to the compounds, but also for discovering new products from uncharacterized BGCs. We established a heterologous expression technique applicable to huge biosynthetic gene clusters for generating large molecular secondary metabolites such as type-I polyketides. As an example, we targeted concanamycin BGC from Streptomyces neyagawaensis IFO13477 (the cluster size of 99 kbp), and obtained a bacterial artificial chromosome (BAC) clone with an insert size of 211 kbp that contains the entire concanamycin BGC. Interestingly, heterologous expression for this BAC clone resulted in two additional aromatic polyketides, ent-gephyromycin, and a new compound designated as JBIR-157, together with the expected concanamycin. Bioinformatic and biochemical analyses revealed that a cryptic biosynthetic gene cluster in this BAC clone was responsible for the production of these type-II polyketide synthases (PKS) compounds. Here, we describe the production, isolation, and structure elucidation of JBIR-157, determined primarily by a series of NMR spectral analyses.

Cell-penetrating peptides (CPPs) serve as potent vehicles for delivering membrane-impermeable compounds, including nucleic acids, into cells. In a previous study, we reported the successful intracellular delivery of small interfering RNAs (siRNAs) with negligible cytotoxicity using a peptide containing an unnatural amino acid (dipropylglycine). In the present study, we employed the same seven peptides as the previous study to evaluate their efficacy in delivering plasmid DNA (pDNA) intracellularly. Although pDNA and siRNA are nucleic acids, they differ in size and biological function, which may influence the optimal peptide sequences for their delivery. Herein, three peptides demonstrated effective pDNA transfection abilities. Notably, only one of the three peptides previously exhibited efficient gene-silencing effect with siRNA. These findings validate our hypothesis and offer insights for the personalized design of CPPs for the delivery of pDNA and siRNA.

Preparation of drug metabolites at the milligram scale is essential for determining the structure and toxicity of drug metabolites. However, their preparation using recombinant proteins and human liver microsomes (HLM) is often difficult because of technical and ethical issues. Reproducing human drug metabolism in food-derived microorganisms may be useful for overcoming these challenges. In this study, we identified an unknown metabolite of the anaesthetic drug lidocaine, which is metabolised by HLM. By screening for lidocaine metabolic activity in five types of foods (blue cheese, shiitake mushroom, natto, yoghurt, and dry yeast), we found that bacteria isolated from natto reproduced the lidocaine metabolic reaction that occurs in HLM. A fraction containing the unknown lidocaine metabolite was prepared through mass cultivation of a Bacillus subtilis standard strain, ethyl acetate extraction, open column chromatography, and HPLC purification. We identified the unknown metabolite as 3-(2,6-dimethylphenyl)-1-ethyl-2-methyl-4-imidazolidinone using NMR. Our results showed that food-derived microorganisms can produce large amounts of human drug metabolites via large-scale cultivation. Additionally, food microorganisms that can reproduce drug metabolism in humans can be used to examine drug metabolites at a low cost and without ethical issues.

Ellagitannins, a class of polyphenols with divergent structures, have attracted considerable attention from synthetic organic chemists. The basic structures in ellagitannins contain esters of D-glucose with galloyl or hexahydroxyldiphenoyl groups, as well as diaryl ether structures. Thus, the synthesis methodologies of such components have been developed by various groups, including our group. This review describes the synthetic methods reported by our group during 2017–2023, aimed at increasing the number of ellagitannins that can be chemically synthesized. In addition, recent related reports are introduced.

Batrachotoxin (1) is a potent cardio- and neurotoxic steroid isolated from certain species of frogs, birds, and beetles. We previously disclosed two synthetic routes to 1. During our synthetic studies toward 1, we explored an alternative strategy for efficiently assembling its 6/6/6/5-membered steroidal skeleton (ABCD-ring). Here we report the application of intermolecular Weix and intramolecular pinacol coupling reactions. While Pd/Ni-promoted Weix coupling linked the AB-ring and D-ring fragments, SmI₂-mediated pinacol coupling did not cyclize the C-ring. Instead, we discovered that SmI₂ promoted a 1,4-addition of the α-alkoxy radical intermediate to produce the unusual 11(9→7)-abeo-steroid skeleton. Thus, this study demonstrates the convergent assembly of the skeleton of the natural product matsutakone in 11 steps from 2-allyl-3-hydroxycyclopent-2-en-1-one.

Tablets are the most commonly used dosage form in the pharmaceutical industry, and their properties such as disintegration, dissolution, and portability are influenced by their strength. However, in industry, the mixing fraction of powders to obtain a tablet compact with sufficient strength is determined based on empirical rules. Therefore, a method for predicting tablet strength based on the properties of a single material is required. The objective of this study was to quantitatively evaluate the relationship between the compression properties and tablet strength of powder mixtures. The compression properties of the powder mixtures with different plasticities were evaluated based on the force-displacement curves obtained from the powder compression tests. Heckel and compression energy analyses were performed to evaluate compression properties. During the compression energy analysis, the ratio of plastic deformation energy to elastic deformation energy (E_p/E_e) was assumed to be the plastic deformability of the powder. The quantitative relationship between the compression properties and tensile strength of the tablets was investigated. Based on the obtained relationship and the compression properties of a single material, a prediction equation was put forward for the compression properties of the powder mixture. Subsequently, a correlation equation for tablet strength was proposed by combining the values of K and E_p/E_e obtained from the Heckel and compression energy analyses, respectively. Finally, by substituting the compression properties of the single material and the mass fraction of the plastic material into the proposed equation, the tablet strength of the powder mixture with different plastic deformabilities was predicted.

A diazo-, metal-, and base-free multi-substituted hydrazone synthesis via a formal reductive N–H bond insertion reactions of hydrazones to α-keto esters has been developed. The protocol features a broad substrate scope and good functional group tolerance, providing N–H bond insertion products in moderate to excellent yields. Moreover, P(III)-mediated N–H functionalization of pharmaceutical containing hydrazone moiety was also successfully achieved.

Codeine is a common analgesic drug that is a pro-drug of morphine. It also has a high risk of abuse as a recreational drug because of its extensive distribution as an OTC drug. Therefore, sensitive and selective screening methods for codeine are crucial in forensic analytical chemistry. To date, a commercial analytical kit has not been developed for dedicated codeine determination, and there is a need for an analytical method to quantify codeine in the field. In the present work, potential modulation was combined with electrochemiluminescence (ECL) for sensitive determination of codeine. The potential modulated technique involved applying a signal to electrodes by superimposing an AC potential on the DC potential. When tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)₃]²⁺) was used as an ECL emitter, ECL activity was confirmed for codeine. A detailed investigation of the electrochemical reaction mechanism suggested a characteristic ECL reaction mechanism involving electrochemical oxidation of the opioid framework. Besides the usual ECL reaction derived from the amine framework, selective detection of codeine was possible under the measurement conditions, with clear luminescence observed in an acidic solution. The sensitivity of codeine detection by potential modulated-ECL was one order of magnitude higher than that obtained with the conventional potential sweep method. The proposed method was applied to codeine determination in actual prescription medications and OTC drug samples. Codeine was selectively determined from other compounds in medications and showed good linearity with a low detection limit (150 ng mL⁻¹).

Generating reliable data on functional group compatibility and chemoselectivity is essential for evaluating the practicality of chemical reactions and predicting retrosynthetic routes. In this context, we performed systematic studies using a functional group evaluation kit including 26 kinds of additives to assess the functional group tolerance of carbene-mediated reactions. Our findings revealed that some intermolecular heteroatom–hydrogen insertion reactions proceed faster than intramolecular cyclopropanation reactions. Lewis basic functionalities inhibited rhodium-catalyzed C–H functionalization of indoles. While performing these studies, we observed an unexpected C–H functionalization of a 1-naphthol variant used as an additive.

An improvement of the two-photon excitation was achieved using 8-azacoumarin-type caged compounds, which showed large values of the two-photon uncaging action cross-section (δ_u >0.1 Goeppert–Mayer (GM)). In particular, the 7-hydroxy-6-iodo-8-azacoumarin (8-aza-Ihc)-caged compound showed an excellent uncaging action cross-section value (δ_u = 1.28 GM). Therefore, 8-azacoumarin-type photolabile protecting groups (PPGs) can be used as two-photon excitation sources.

Polymeric nanofibers generated via electrospinning offer a promising platform for drug delivery systems. This study examines the application of electrospun polyvinyl alcohol (PVA) nanofibers for controlled lysozyme (LZM) delivery. By using various PVA grades, such as the degree of polymerization/hydrolysis, this study investigates their influence on nanofiber morphology and drug-release characteristics. LZM-loaded PVA monolithic nanofibers having 50% drug content exhibit efficient entrapment, wherein rapid dissolution is achieved within 30 min. The initial burst of LZM from the nanofiber was reduced as the LZM content was lowered. The initial dissolution is greatly influenced by the choice of PVA grade used; fully hydrolyzed PVA nanofibers demonstrate controlled release due to the reduced water solubility of PVA. Furthermore, coaxial electrospinning, which creates core–shell nanofibers with polycaprolactone as a controlled release layer, enables sustained LZM release over an extended period. This study confirms a correlation between PVA characteristics and controlled drug release and provides valuable insights into tailoring nanofiber properties for pharmaceutical applications.

This study showcases the 1,2-migration reactions of alkyl and aryl groups on the indole molecule. Trifluoromethanesulfonic acid effectively facilitates the migration of the substituent from C3- to C2-position of the indole structure. The resulting C2-substituted indoles offer a valuable pathway for the synthesis of natural products and medicinal compounds.

Vizantin, 6,6′-bis-O-(3-nonyldodecanoyl)-α,α′-trehalose, has been developed as a safe immunostimulator on the basis of a structure–activity relationship study with trehalose 6,6′-dicorynomycolate. Our recent study indicated that vizantin acts as an effective Toll-like receptor-4 (TLR4) partial agonist to reduce the lethality of an immune shock caused by lipopolysaccharide (LPS). However, because vizantin has low solubility in water, the aqueous solution used in in vivo assay systems settles out in tens of minutes. Here, vizantin was chemically modified in an attempt to facilitate the preparation of an aqueous solution of the drug. This paper describes the concise synthesis of a water-soluble vizantin analogue in which all the hydroxyl groups of the sugar unit were replaced by sulfates. The vizantin derivative displayed micelle-forming ability in water and potent TLR-4 partial agonist activity.

Nucleophilic deprotection of p-methoxybenzyl (PMB) [p-methoxyphenylmethyl (MPM)] ethers was developed using a heterogeneous oxovanadium catalyst V-MPS4 and a thiol nucleophile. The deprotection method had a wide reaction scope, including PMB ethers of primary, secondary, and tertiary alcohols bearing various functional groups. In addition, the PMB ether of an oxidation-labile natural product was successfully removed by V-MPS4 catalysis, while a common oxidative method of PMB deprotection afforded a complex mixture. The V-MPS4 catalyst was reusable up to six times without a significant loss in the product yield. The advantages of using the heterogeneous catalyst were further demonstrated by conducting the deprotection reaction in a continuous flow process, which resulted in a 2.7-fold higher catalyst turnover number and 60-fold higher turnover frequency compared to those of the corresponding batch reaction.