The new chalcogenylation of phosphines using ⁿBu₄N‧XCN (X = S, Se) is described. The reaction in 1,2-dichloroethane at 120 °C provided the corresponding phosphine sulfides in good to high yields. The protocol could be extended to the synthesis of phosphinic acid derivatives as well as sulfurization of poly(styrene-co-4-styryldiphenylphosphine).

α-Alkoxy bridgehead radicals enable intermolecular construction of sterically congested C–C bonds due to their sterically accessible nature. We implemented these radical species into total syntheses of various densely oxygenated natural products and demonstrated their exceptional versatility. Herein, we employed different precursors to generate the same α-alkoxy bridgehead radical and compared the efficacy of the precursors for coupling reactions. Specifically, the bridgehead radical of the trioxaadamantane structure was formed from α-alkoxy carboxylic acid, selenide/telluride, and acyl selenide/acyl telluride, and reacted with 4-((tert-butyldimethylsilyl)oxy)cyclopent-2-en-1-one and 5-oxo-1-cyclopentene-1-carbonitrile. The efficiency of the bridgehead radical formation and subsequent coupling reaction significantly depended on the structures of the precursors and acceptors as well as the reaction conditions. Our findings provide new insights for selecting the appropriate substrates of key coupling reactions in the total synthesis of complex natural products.

We report chemoselective hydrogenation of α,β-unsaturated anilides catalyzed by the palladium-polymethylhydrosiloxane (hydrosilane) system. Under this condition, C–C double bonds are selectively reduced while other reducible groups such as acetyl groups, nitro groups, nitriles, benzyl ethers, and halogens are largely tolerated. This chemoselective hydrogenation is promising for the development of efficient synthetic routes for multi-functional compounds.

In recent years, there has been a growing focus on the development of medium-sized drugs based on peptides or nucleic acids owing to their potential therapeutic benefits. As some of these medium-sized drugs exert their therapeutic effects by adopting specific secondary structures, evaluating their conformational states is crucial to ensure the efficacy, quality, and safety of the drug products. It is important to assess the structural integrity of biomolecular therapeutics to guarantee their intended pharmacological activity and maintain the required standards for drug development and manufacturing. One widely utilized technique for quality evaluation is secondary structural analysis using circular dichroism (CD) spectroscopy. Given the higher production and quality control costs associated with medium-sized drugs compared with small-molecule drugs, developing analytical techniques that enable CD analysis with reduced sample volumes is highly desirable. Herein, we focused on a microsampling disk-type cell as a potential solution for reducing the required sample volume. We investigated whether CD spectral analysis using a microsampling disk could provide equivalent spectra compared with the standard cell (sample volume: approx. 300 µL). Our findings demonstrated that the microsampling disk (sample volume: 2–10 µL) could be successfully applied to CD spectral analysis of peptide and nucleic acid drugs, paving the way for more efficient and cost-effective quality evaluation processes.

The purpose of this study was to continuously monitor the pseudopolymorphic transition from anhydrate to monohydrate by measuring the NMR relaxation using time-domain NMR (TD-NMR). Taking advantage of the simplicity of the low-field NMR instrument configuration, which is an advantage of TD-NMR, the NMR instrument was connected to a humidity controller to monitor the pseudopolymorphic transition. First, ezetimibe (EZT) monohydrate was prepared from its anhydrate using a saturated salt solution method, and T₁ relaxation of EZT monohydrate and anhydrate was measured without a humidity controller. The T₁ relaxation results confirmed that EZT anhydrate and monohydrate could be distinguished using T₁ relaxation measurement. Next, continuous monitoring was conducted by TD-NMR and connected to a humidity controller. Anhydrous EZT was placed in an NMR glass tube and the T₁ relaxation measurement was repeated while maintaining the humidity on the side entering the NMR tube at 80% relative humidity. The T₁ relaxation became gradually faster from the initial to middle monitoring phases. The final T₁ relaxation was then recovered fully and these T₁ relaxation times were the same as the T₁ relaxation of EZT monohydrate. This study successfully monitored the pseudopolymorphic transition from EZT anhydrate to monohydrate via NMR relaxation.

Here, we report the first synthesis of oxyphyllin A/belchinoid A, a 7,9-seco-8,12-dinor-guaiane sesquiterpene whose isolation was reported independently by two groups in 2023. This synthesis utilizes a key sequential sulfone-mediated intermolecular alkylation/5-endo-tet cyclization reaction to establish the C1, C4, C5 stereocenters. Subsequent transformations, including regio- and stereoselective hydride addition-based desulfonylation via a π–allyl palladium complex and the Wittig reaction with a stable phosphonium ylide, facilitated the synthesis of oxyphyllin A/belchinoid A.

We report two methods for the preparation of peptide thioesters containing Tyr(SO₃H) residue(s), without use of a protecting group for the sulfate moiety. The first was based on direct thioesterification using carbodiimide on a fully protected peptide acid, prepared on a 2-chlorotrityl (Clt) resin with fluoren-9-ylmethoxycarbonyl (Fmoc)-based solid-phase peptide synthesis (Fmoc-SPPS). Subsequent deprotection of the protecting groups with trifluoroacetic acid (TFA) (0 °C, 4 h) yielded peptide thioesters containing Tyr(SO₃H) residue(s). Peptide thioesters containing one to three Tyr(SO₃H) residue(s), prepared by this method, were used as building blocks for the synthesis of the N^α-Fmoc-protected N-terminal part of P-selectin glycoprotein ligand 1 (PSGL-1) (Fmoc-PSGL-1(43–74)) via silver-ion mediated thioester segment condensation. The other method was based on the thioesterification of peptide azide, derived from a peptide hydrazide prepared on a NH₂NH-Clt-resin with Fmoc-SPPS. Peptide thioester containing two Tyr(SO₃H) residues, prepared via this alternative method, was used as a building block for the one-pot synthesis of the N-terminal extracellular portion of CC-chemokine receptor 5 (CCR5(9–26)) by native chemical ligation (NCL). The two methods for the preparation of peptide thioesters containing Tyr(SO₃H) residue(s) described herein are applicable to the synthesis of various types of sulfopeptides.

Although opioid analgesics are indispensable in treating pain, these drugs are accompanied by life-threatening side effects. While clinically relevant opioid drugs target the µ opioid receptor (MOR), a heterodimer between the MOR and the δ opioid receptor (DOR) has emerged as another target to develop safer analgesics. Although some heterodimer-preferring agonists have been reported so far, it is still difficult to activate the MOR/DOR heterodimer selectively in the presence of MOR or DOR monomers/homodimers. To gain insights to develop selective agonists for MOR/DOR, herein we prepared analogs of CYM51010, one of the reported heterodimer-preferring agonists, and collected structure–activity relationship information. We found that the ethoxycarbonyl group was needed for the activity for the heterodimer, although this group could be substituted with functional groups with similar sizes, such as an ethoxycarbonyl group. As for the acetylaminophenyl group, not a type of substituent, but rather a substituent located at a specific position (para-position) was essential for the activity. Changing the linker length between the acetylaminophenyl group and the piperidine moiety also had deleterious effects on the activity. On the other hand, the substitution of the acetylamino group with a trifluoroacetylamino group and the substitution of the phenethyl group with a benzyl group diminished the activities for the monomers/homodimers while keeping the activity for MOR/DOR, which enhanced the selectivity. Our findings herein will play an important role in developing selective agonists for MOR/DOR and for elucidating the physiological roles of this heterodimer in analgesic processes and in the establishment of side effects.

The biosynthetic pathways of natural products are complicated, and it is difficult to fully elucidate their details using experimental chemistry alone. In recent years, efforts have been made to elucidate the biosynthetic reaction mechanisms by combining computational and experimental methods. In this review, we will discuss the biosynthetic studies using computational chemistry for various terpene compounds such as cyclooctatin, sesterfisherol, quiannulatene, trichobrasilenol, asperterpenol, preasperterpenoid, spiroviolene, and mangicol.

Lipid nanoparticles (LNPs), used for mRNA vaccines against severe acute respiratory syndrome coronavirus 2, protect mRNA and deliver it into cells, making them an essential delivery technology for RNA medicine. The LNPs manufacturing process consists of two steps, the upstream process of preparing LNPs and the downstream process of removing ethyl alcohol (EtOH) and exchanging buffers. Generally, a microfluidic device is used in the upstream process, and a dialysis membrane is used in the downstream process. However, there are many parameters in the upstream and downstream processes, and it is difficult to determine the effects of variations in the manufacturing parameters on the quality of the LNPs and establish a manufacturing process to obtain high-quality LNPs. This study focused on manufacturing mRNA-LNPs using a microfluidic device. Extreme gradient boosting (XGBoost), which is a machine learning technique, identified EtOH concentration (flow rate ratio), buffer pH, and total flow rate as the process parameters that significantly affected the particle size and encapsulation efficiency. Based on these results, we derived the manufacturing conditions for different particle sizes (approximately 80 and 200 nm) of LNPs using Bayesian optimization. In addition, the particle size of the LNPs significantly affected the protein expression level of mRNA in cells. The findings of this study are expected to provide useful information that will enable the rapid and efficient development of mRNA-LNPs manufacturing processes using microfluidic devices.

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.