The readthrough mechanism, which skips the premature termination codon and restores the biosynthesis of the defective enzyme, is an emerging therapeutic tactic for nonsense mutation-related diseases, such as Hurler syndrome, a type of mucopolysaccharidosis. In the present study, novel triaryl derivatives were synthesized and their readthrough-inducing activities were evaluated by a luciferase reporter assay with a partial α-L-iduronidase (IDUA) DNA sequence containing the Q70X nonsense mutation found in Hurler syndrome and by measuring the enzyme activity of IDUA knockout cells transfected with the mutant IDUA gene. KY-516, a representative compound in which the meta position carboxyl group of the left ring of the clinically used ataluren was converted to the para position sulfamoylamino group, the central ring to triazole, and the right ring to cyanobenzene, exhibited the most potent readthrough-inducing activity in the Q70X/luciferase reporter assay. In Q70X mutant IDUA transgenic cells, KY-516 significantly increased enzyme activity at 0.1 µM. After the oral administration of KY-516 (10 mg/kg), the highest plasma concentration of KY-516 was above 5 µM in rats. These results indicate that KY-516, a novel triaryl derivative, exhibits potent readthrough-inducing activity and has potential as a therapeutic agent for Hurler syndrome.

As an extension of our research on providing a chemical library of side-chain fluorinated vitamin D₃ analogues, we newly designed and synthesized 26,27-difluoro-25-hydroxyvitamin D₃ (1) and 26,26,27,27-tetrafluoro-25-hydroxyvitamin D₃ (2) using a convergent method applying the Wittig–Horner coupling reaction between CD-ring ketones (13, 14) and A-ring phosphine oxide (5). The basic biological activities of analogues, 1, 2, and 26,26,26,27,27,27-hexafluoro-25-hydroxyvitamin D₃ [HF-25(OH)D₃] were examined. Although the tetrafluorinated new compound 2 exhibited higher binding affinity for vitamin D receptor (VDR) and resistance to CYP24A1-dependent metabolism compared with the difluorinated 1 and its non-fluorinated counterpart 25-hydroxyvitamin D₃ [25(OH)D₃], HF-25(OH)D₃ showed the highest activity among these compounds. Osteocalcin promoter transactivation activity of these fluorinated analogues was tested, and it decreased in the order of HF-25(OH)D₃, 2, 1, and 25(OH)D₃ in which HF-25(OH)D₃ showed 19-times greater activity than the natural 25(OH)D₃.

Jadomycins, which are benzo[b]phenanthridine-type alkaloids isolated from Streptomyces venezuelae ISP5230, exhibit cytotoxic activity against multidrug-resistant breast cancer cells. We have previously achieved the total synthesis of jadomycins using the direct arylation of juglone as a key step. In this study, we achieved the total synthesis of jadomycin T and jadomycin aglycons using L-threonine and 1-amino-2-propanol as nitrogen sources. Additionally, we evaluated the cytotoxic activity of eight compounds, including glycosides, jadomycin T, and their corresponding aglycons, in eight types of tumor cells. The evaluated jadomycins tended to exhibit stronger cytotoxic activity as aglycons than as glycosides. Although the presence of a 1,3-oxazolidine ring derived from an amino acid was not essential, the presence of the 1,3-oxazolidine ring showed strong activity when the ring had a carboxyl group. Furthermore, compared to the non-natural isomer at a different position on the phenolic hydroxyl group, the naturally occurring phenanthroviridin aglycon exhibited stronger cytotoxic activity. In addition, this study suggests that jadomycins may become lead compounds for the treatment of brain tumors; however, further studies on their ability to penetrate the blood–brain barrier are required.

To develop dearomatization reactions based on a nucleophilic activation of phenols, naphthols, and indoles, ipso-Friedel–Crafts-type C-alkylation must be selectively promoted over competitive O- or N-alkylation reactions. Resolving this chemoselectivity issue is essential for developing this class dearomatization reaction. We found that various dearomatization reactions could be developed using appropriately designed aromatic substrates with an electrophilic moiety for intramolecular reactions. This review describes the transition-metal-catalyzed dearomatization reactions developed by our group. π-Allylpalladium species, η³-propargylpalladium species, alkynes activated by Au(I) species, and silver carbene species could be applied as electrophiles in our reaction system, which provided access to a wide variety of dearomatized products from planar aromatic compounds in a highly chemoselective manner.

Although aryl hydrocarbon receptors (AhRs) are related to the metabolic pathway of xenobiotics, recent studies have revealed that this receptor is also associated with the life cycle of viruses and inflammatory reactions. For example, flutamide, used to treat prostate cancer, inhibits hepatitis C virus proliferation by acting as an AhR antagonist, and methylated-pelargonidin, an AhR agonist, suppresses pro-inflammatory cytokine production. To discover a novel class of AhR ligands, we screened 1000 compounds derived from fungal metabolites using a reporter assay and identified methylsulochrin as a partial agonist of the aryl hydrocarbon receptor. Methylsulochrin was found to inhibit the production of hepatitis C virus (HCV) in Huh-7.5.1 cells. Methylsulochrin also suppressed the production of interleukin-6 in RAW264.7 cells. Furthermore, a preliminary structure–activity relationship study using sulochrin derivatives was performed. Our findings suggest the use of methylsulochrin derivatives as anti-HCV compounds with anti-inflammatory activity.

A strategy for symmetric synthesis based on dynamic chirality of enolates (memory of chirality) has been developed. Asymmetric alkylation, conjugate addition, aldol reaction, and arylation via C–N axially chiral enolate intermediates are described. Asymmetric alkylation and conjugate addition via C–O axially chiral enolate intermediates with a half-life of racemization as short as approx. 1 s. at −78 °C have been accomplished. Organocatalysts for asymmetric acylation and site-selective acylation have been developed. Kinetic resolution of racemic alcohols via remote asymmetric induction by the catalyst is shown. Catalyst-controlled site-selective acylation of carbohydrates and its application to total synthesis of natural glycoside are described. Chemo-selective monoacylation of diols and selective acylation of secondary alcohols with reversal of inherent reactivity are also discussed. Geometry-selective acylation of tetrasubstituted alkene diols is achieved, where acylation takes place independent from the steric environments of the substrates.

Time-domain NMR (TD-NMR) was used for continuous monitoring of the hydration behavior of hydrophilic matrix tablets. The model matrix tablets comprised high molecular weight polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC), and polyethylene glycol (PEG). The model tablets were immersed in water. Their T₂ relaxation curves were acquired by TD-NMR with solid-echo sequence. A curve-fitting analysis was conducted on the acquired T₂ relaxation curves to identify the NMR signals corresponding to the nongelated core remaining in the samples. The amount of nongelated core was estimated from the NMR signal intensity. The estimated values were consistent with the experiment measurement values. Next, the model tablets immersed in water were monitored continuously using TD-NMR. The difference in hydration behaviors of the HPMC and PEO matrix tablets was then characterized fully. The nongelated core of the HPMC matrix tablets disappeared more slowly than that of the PEO matrix tablets. The behavior of HPMC was significantly affected by the PEG content in the tablets. It is suggested that the TD-NMR method has potential to be utilized to evaluate the gel layer properties, upon replacement of the immersion medium: purified (nondeuterated) water is replaced with heavy (deuterated) water. Finally, drug-containing matrix tablets were tested. Diltiazem hydrochloride (a highly water-soluble drug) was employed for this experiment. Reasonable in vitro drug dissolution profiles, which were in accordance with the results from TD-NMR experiments, were observed. We concluded that TD-NMR is a powerful tool to evaluate the hydration properties of hydrophilic matrix tablets.

Our group has reported various derivatives of lysophosphatidylserine (LysoPS) as potent and subtype-selective agonists for G-protein-coupled receptors (GPCRs). However, the ester linkage between the glycerol moiety and fatty acid or fatty acid surrogate is present in all of them. In order to develop these LysoPS analogs as drug candidates, appropriate pharmacokinetic consideration is essential. Here, we found that the ester bond of LysoPS is highly susceptible to metabolic degradation in mouse blood. Accordingly, we examined isosteric replacement of the ester linkage with heteroaromatic rings. The resulting compounds showed excellent retention of potency and receptor subtype selectivity, as well as increased metabolic stability in vitro.

We have developed a new one-pot disulfide-driven cyclic peptide synthesis. The entire process is carried out in the solid phase, thus eliminating complicated work up procedures to remove by-products and unreacted reagents and enabling production of high-purity cyclic disulfide peptides by simple cleavage of a peptidyl resin. The one-pot synthesis of oxytocin was accomplished in this way with an isolated yield of 28% over 13 steps. These include peptide chain elongation from an initial resin, sulfenylation of the protected side chain of a cysteine (Cys) residue, disulfide ligation between thiols in an additional peptide fragment and a 3-nitro-2-pyridinesulfenyl-protected cysteine (Cys(Npys))-containing peptide resin, subsequent intramolecular amide bond formation of the disulfide-connected fragments by an Ag⁺-promoted thioester method, followed by deprotection and HPLC purification.

Good adherence to medication is critical for successfully treating psychiatric disorders. Tailor-made pharmaceutical formulations can provide a suitable dosage form to meet the specific needs of individual patients who exhibit poor adherence to industrially manufactured products. Herein, we prepared aripiprazole (ARP) gummies (ARP-Gs) using a commercially available ARP formulation. We aimed to clarify the palatability of ARP-Gs by performing a gustatory sensation test in healthy volunteers. We performed two types of organoleptic masking of ARP-Gs, cocoa- and fruit-flavoured gummies (6.0 mg of ARP/3.5 g of gummy), and conducted two different gustatory sensation tests for each ARP-G. Ten young, healthy volunteers (mean ± standard deviation, 23.7 ± 1.2 years) were enrolled in each trial. The overall palatability of ARP-Gs was evaluated using the 100-mm visual analogue scale (VAS). Receiver operating characteristic (ROC) curve analysis was performed between VAS scores of total ARP-G palatability and acceptability assessed using a 5-point rating scale. Among cocoa-flavoured ARP-Gs, those combining aspartame, cocoa powder, and banana flavour (ABC-ARP-G) exhibited the highest VAS scores for total palatability. Similarly, the VAS scores of grapefruit-flavoured ARP-Gs (GF-ARP-G) showed the highest values considering all fruit-flavoured ARP-Gs. The VAS scores for ABC-ARP-G and GF-ARP-G greatly exceeded the cut-off values of acceptability calculated using the ROC curve. We developed two types of ARP-Gs with organoleptic masking as tailor-made pharmaceutical formulations. ABC-ARP-Gs and GF-ARP-Gs could be acceptable in patients. ARP-Gs could be an alternative to currently available pharmaceutical formulations to enhance their adherence and meet the specific needs of individual patients.

Nitric oxide (NO) has multiple physiological activities, including roles in vasorelaxation, neurotransmission, and immune response. Indeed, NO-releasing compounds are utilized as therapeutic agents for cardiovascular diseases based on the potent and rapid vasorelaxation induced by NO. We have developed a series of photoinduced-electron-transfer-driven (PeT-driven) NO releasers composed of a light-harvesting antenna moiety and an NO-releasing N-nitrosoaminophenol moiety, which efficiently release NO upon irradiation with blue (500 nm), green (560 nm), or red (650 nm) light. In this paper, we investigated substituent effects at the 2-position of the N-nitrosoaminophenol moiety by means of spectroscopic, fluorescence, and NO-release measurements. Interestingly, a methyl substituent at this position had no significant effect on the NO-releasing ability, while a nitro group or a methoxy group reduced it. The nitro group may suppress electron transfer to the antenna moiety, while the methoxy group may accelerate electron transfer but suppress deprotonation to afford the phenoxyl radical, which is the key reaction for release of NO. These structure–activity relationships should be helpful for further functionalizing PeT-driven NO releasers.

With the aim of achieving the convergent elongation of peptide chains, an amide bond formation reaction that enables a peptide fragment coupling has long been pursued. The decarboxylative amidation recently reported by our group is a potential solution to this problem. In this article, a mechanistic analysis of the t-butyl hydroperoxide (TBHP) mediated-decarboxylative amidation of α-ketoacids that results in a significant advance in convergent peptide synthesis is described. Despite the observation of epimerization with low bulk substrates in preliminary studies, a systematic examination and understanding of the reaction mechanism enabled the development of a modified epimerization-free reaction whereby peptide fragment couplings using peptide α-ketoacids were successfully achieved.

Dried and fermented (processed) leaves of Hydrangea macrophylla Seringe var. thunbergii Makino (Hydrangeae Dulcis Folium) are currently used as a crude drug with a sweet taste for diabetic patients and as an oral refrigerant. The sweet taste of this crude drug is primarily attributed to phyllodulcin. However, there are currently no standards for the cultivation of H. macrophylla var. thunbergii and the isolation and production of the primary constituents of this crude drug. In the present study, we prepared five types of soils with different pH values (pH 7.5–5.0) and investigated the effects of these soils on the growth of this plant. The contents of phyllodulcin and its glycoside, phyllodulcin 8-O-β-D-glucopyranoside, in the leaves of plants grown in these soils were quantified. Furthermore, the correlation between the sweetness of Hydrangeae Dulcis Folium and phyllodulcin was investigated. The results showed that soils with pH ranging from 7.0 to 5.5 was not only suitable for plant growth but also increased the content of phyllodulcin and phyllodulcin 8-O-β-D-glucopyranoside in the leaves. Altogether, these findings could be useful for the development of high-quality Hydrangeae Dulcis Folium.

Oral disulfiram (DSF) has been used clinically for alcohol dependence and recently has been found to have antitumor activity. A transdermal delivery system would be useful for maintaining drug concentration and reducing the frequency of administration of DSF for cancer treatment. Penetrating the stratum corneum (SC) barrier is a challenge to the transdermal delivery of DSF. Therefore, we investigated the promoting effects and mechanism of action of the combination of oleic acid (OA) and Tween 80 on the skin permeation of DSF. Hairless mouse skin was exposed to OA and Tween 80, combined in various ratios (1 : 0, 2 : 1, 1 : 1, 1 : 2, and 0 : 1). A permeation experiment was performed, and total internal reflection IR spectroscopic measurements, differential scanning calorimetry, and synchrotron radiation X-ray diffraction measurements were taken of the SC with each applied formulation. The combination of OA and Tween 80 further enhanced the absorption-promoting effect of DSF, compared with individual application. The peak of the CH₂ inverse symmetric stretching vibration near the skin surface temperature was shifted by a high frequency due to the application of OA, and DSF solubility increased in response to Tween 80. We believe that the increased fluidity of the intercellular lipids due to OA and the increased solubility of DSF due to Tween 80 promoted the absorption of DSF. Our study clarifies the detailed mechanism of action of the skin permeation and promoting effect of DSF through the combined use of OA and Tween 80, contributing to the development of a transdermal preparation of DSF.

The fragment molecular orbital (FMO) method is a fast quantum-mechanics method that divides systems into pieces of fragments and performs ab initio calculations. The method has been expected to improve the accuracy of describing protein-ligand interactions by incorporating electronic effects. In this article, FMO calculation with solvation methods were applied to the affinity prediction at the ATP-binding site of PDHK4. As the ionized aspartic acid lies at the center and is involved in the complex hydrogen bond networks, this system has turned out to be a difficult target to describe by traditional molecular-mechanics method. In the FMO calculation with the polarizable continuum model (PCM) solvation method, a considerable amount of charge (−0.27e) was transferred from the ionized aspartate to the surrounding residues. We found that using FMO with the PCM solvation method was important to increase the correlation, and by incorporating the ligand deformation energy, the correlation was improved to R = 0.81 for whole twelve compounds and R = 0.91 without one outlier compound.

The purpose of the present study was to provide the experimental and theoretical basis of bioequivalence (BE) dissolution test criteria for formulation development of high solubility-low permeability drugs. According to the biowaiver scheme based on the biopharmaceutics classification system (BCS), for BCS class III drugs, a test formulation and a reference formulation are predicted to be BE when 85% of the drug dissolves within 15 min (T_85% < 15 min) in the compendial dissolution test. However, previous theoretical simulation studies have suggested that this criterion may possibly be relaxed for use in practical formulation development. In the present study, the dissolution profiles of 14 famotidine formulations for which BE has been clinically confirmed were evaluated by the compendial dissolution test at pH 1.2 and 6.8. The plasma concentration–time profiles of famotidine formulations were simulated using the dissolution data. In addition, virtual simulations were performed to estimate the range of dissolution rates to be bioequivalent. The fastest and slowest dissolution rates among the famotidine formulations were T_85% = 10 min and T_85% = 60 min at pH 6.8, respectively. The virtual simulation BE study suggested that famotidine formulations can be bioequivalent when T_85% < 99 min. In the case of BCS III drugs, the rate-limiting step of oral drug absorption is the membrane permeation process rather than the dissolution process. Therefore, a difference in the dissolution process has less effect on BE. These results contribute to a better understanding of the biowaiver approach and would be of great help in the formulation development of BCS class III drugs.

It is generally accepted that the orexin 2 receptor (OX₂R) plays a critical role in the arousal-promoting function, and in vivo imaging of OX₂R is expected to contribute to elucidation of orexin systems and the development of drugs to treat sleep disorder. In this study, we newly synthesized and characterized a radioiodinated triazole-pyrolidine derivative ([¹²⁵I]TPI) to detect OX₂R in the brain. In vitro studies using OX₁R or OX₂R expression cells showed selective binding of [¹²⁵I]TPI to OX₂R. In addition, in vitro autoradiography using rat brain sections showed high accumulation of radioactivity in the OX₂R expression region. However, [¹²⁵I]TPI showed low brain uptake in normal mice. These results suggest that [¹²⁵I]TPI has a fundamental character to detect OX₂R in vitro, but further structural modification to improve brain pharmacokinetics is required to use it for in vivo detection of OX₂R.

Amphipathic peptides composed of cationic amino acids and hydrophobic amino acids have cell-penetrating ability and are often used as a delivery tool for membrane-impermeable compounds. Small interfering RNA (siRNAs) are one of the delivery targets for such cell-penetrating peptides (CPPs). Cationic CPPs can associate with anionic siRNAs by electrostatic interactions resulting in the formation of nano-sized complexes, which can deliver siRNAs intracellularly. CPPs containing unnatural amino acids offer promising tools to siRNA delivery. However, the detailed structure–activity relationship in siRNA delivery has been rarely studied. In the current study, we designed peptides containing dipropylglycine (Dpg) and explored the cellular uptake and cytotoxicity of peptide/siRNA complexes. The amphipathic structure of the peptides played a key role in complexation with siRNAs and intracellular siRNA delivery. In the amphipathic peptides, cellular uptake of siRNA increased with increasing peptide length, but cytotoxicity was reduced. A peptide containing four Dpg exhibited an effective gene-silencing effect with small amounts of peptides without cytotoxicity in medium containing serum. These findings will be helpful for the design of novel CPPs for siRNA delivery.

Mechanistic target of rapamycin (mTOR) is an effective anti-tumor drug target. Several mTOR kinase inhibitors have entered clinical research, but there are still challenges of potential toxicity. As a new type of targeted drug, proteolysis targeting chimeras (PROTACs) have features of low dosage and low toxicity. However, this approach has been rarely reported to involve mTOR degradation. In this study, the mTOR kinase inhibitor MLN0128 was used as the ligand to the protein of interest and conjugated with pomalidomide by diverse intermediate linkage chains. Several potential small molecule PROTACs for the degradation of mTOR were designed and synthesized. PROTAC compounds exhibited mTOR inhibitory activity and suppressed MCF-7 cell proliferation. The representative compound P1 could inhibit the expression of mTOR downstream proteins and the growth of cancer cells by inducing autophagy but not affecting the cell cycle and not inducing apoptosis.