The acetamide moiety is a general functional group present in many natural and pharmaceutical products. Herein, we report two new reagents, p-methoxybenzyl N-acetylcarbamate potassium salt (PM-BENAC-K) and 2,4-dimethoxybenzyl N-acetylcarbamate potassium salt (2,4-DM-BENAC-K), which are refined versions of the benzyl N-acetylcarbamate potassium salt (BENAC-K). These compounds, which we reported as simple equivalents of N-acetamide nucleophiles, are stable and easy-to-handle powders that react with a variety of alkyl halides and sulfonates to afford substituted products in good yields. The products were transformed into N-alkylacetamides after p-methoxybenzyloxycarbonyl (Moz) or 2,4-dimethoxybenzyloxycarbonyl (Dmoz) cleavage under mild acidic conditions. The acetyl groups in the substituted products of PM- and 2,4-DM-BENAC-Ks were removed using K₂CO₃ in methanol to afford Moz- and Dmoz-protected amines, respectively. Hence, the new BENAC-Ks acted as versatile equivalents of both N-acetamide and Moz/Dmoz-protected nitrogen nucleophiles and can be used in synthetic studies of natural and pharmaceutical products.

A number of alkaloids found in Mitragyna species belonging to the Rubiaceae family have been shown to have potent biological activity such as analgesic properties. Here, we report the asymmetric total syntheses of mitragynine, speciogynine, and 7-hydroxymitragynine, which are classified as corynantheine-type monoterpenoid indole alkaloids, isolated from Mitragyna speciosa. These syntheses were accomplished within 12 steps and in >11% total yield from commercial 3-(trimethylsilyl)propanal using an organocatalytic anti-selective Michael reaction and bioinspired transformations.

Herein, we developed secondary-alcohol-selective C–H alkylation of 1,3-butane diol by combining an acridinium photoredox catalyst and a thiophosphoric acid hydrogen atom transfer (HAT) catalyst. The use of non-coordinating solvent such as dichloromethane (DCM) improved secondary α-alkoxy C–H selectivity by lowering bond dissociation energy (BDE) through intramolecular hydrogen bonding.

Hardness is a critical quality characteristic of pharmaceutical oral jelly. In this study, the hardness was determined by using the T₂ relaxation curves measured by time-domain NMR. For sample preparation, kappa- and iota-carrageenans, and locust bean gum, were used as gel-forming agents. Ten test jellies with different gel-forming agent composition were prepared, and their hardness and T₂ relaxation curves were measured by a texture analyzer and time-domain NMR (TD-NMR). A negative correlation between T₂ relaxation time (T₂) and hardness was observed; however, it was difficult to determine the hardness directly from the T₂ value. That is probably because the T₂ relaxation curve contains information about molecular states, not only of water but also of the solute, and T₂ values calculated by single-exponential curve fitting only express one property of the test jelly. By considering this issue, partial least squares (PLS) regression analysis was performed on the T₂ relaxation curves for hardness determination of the test jellies. According to the analysis, an accurate and reliable PLS model was created that enabled accurate assessment of the hardness of the test jellies. TD-NMR enables the measurement of samples nondestructively and rapidly with low cost, and so could be a promising method for evaluation of the hardness of pharmaceutical oral jellies.

We report aryne generation from 2-triazenylarylboronic acids using an activator such as Brønsted acids, Lewis acids, and solid acids. With the use of (±)-Camphorsulfonic acid [(±)-CSA], the aryne precursors provided cycloadducts with a range of arynophiles in high yields. Aryne generated under the acidic conditions underwent chemoselective cycloaddition with a furan in the presence of a basic arynophile, namely an amine. Hammett plot analyses revealed that an aryne generation mechanism induced by (±)-CSA is distinct from the mechanism induced by silica gel.

A lot of chiral stationary phases (CSPs) have been introduced for the purpose of analytical and preparative separations of enantiomers. CSPs based on proteins and glycoproteins have unique properties among those CSPs. This review article deals with the preparation of CSPs based on proteins and glycoproteins, their chiral recognition properties and mechanisms, focusing on the CSPs investigated in our group. The dealt proteins and glycoproteins are including bovine serum albumin, human serum albumin, lysozyme, pepsin, human α₁-acid glycoprotein (AGP), chicken ovomucoid and chicken ovoglycoprotein (named chicken AGP).

Due to the importance of the RNA chemical modifications, methods for the selective chemical modification at a predetermined site of the internal position of RNA have attracted much attention. We have developed functional artificial nucleic acids that modify a specific site of RNA in a site- and base-selective manner. In addition, the copper-catalyzed azide-alkyne cycloaddition (CuAAC) has been shown to introduce additional molecules on the alkynes attached to the pyridine ring. However, it was found that some azide compounds produced the cycloadduct in lower yields. Therefore, in this study, we synthesized the pyridinyl transfer group with the alkyne attached via a polyethylene glycol (PEG) linker with a different length and optimized its structure for both the transfer and CuAAC reaction. Three new transfer groups were synthesized by introducing an alkyne group at the end of the triethylene (11), tetraethylene (12) or pentaethylen glycol linker (13) at the 5-position of the pyridine ring of (E)-3-iodo-1-(pyridin-2-yl)prop-2-en-1-one. These transfer groups were introduced to the 6-thioguanine base in the oligodeoxynucleotide (ODN) in high yields. The transfer groups 11 and 12 more efficiently underwent the cytosine modification. For the CuAAC reaction, although 7 showed low adduct yields with the anionic azide compound, the new transfer groups, especially 12 and 13, significantly improved the yields. In conclusion, the transfer groups 12 and 13 were determined to be promising compounds for the modification of long RNAs.

Cationic liposomal formulations of the telomeric G-quadruplex stabilizing ligand, 13-(2-naphthylmethoxy)berberine bromide (1), have been developed with the purpose of delivering 1 into the nucleus of cancer cells for potential telomere targeting. Berberine derivative 1 was encapsulated in various cationic lipids 2–4 by the thin film evaporation method; these lipids are cationic after amine protonation. The most appropriate liposomal berberine formulation was that of 1 and the cholesterol derived cationic lipid 4 in a weight ratio of 1 : 20 with 76.5% encapsulation efficiency of 1. Cellular uptake studies in the HeLa and HT-29 cancer cells lines showed that the liposomal berberine derivative uptake in the cells was higher and more stable than for berberine derivative 1 alone while free 1 was completely decomposed in the cells within 60 min exposure to the cells. Anticancer activity of the liposomal berberine derivative 1 based on 4 was greater than that for the free berberine derivative 1 in the MCF-7, HeLa and HT-29 cell line by 2.3-, 4.9- and 5.3-fold, respectively, and also, interestingly, superior to the anticancer drug doxorubicin against the HT29 cancer cell line.

Picrotoxinin, coriamyrtin, and tutin are representative natural products classified as picrotoxane-type sesquiterpenes and they function as strong neurotoxins. Because they possess a cis-fused 5,6-ring skeleton with a highly congested functionalization, organic chemistry researchers have pursued the development of a stereoselective synthesis method for such skeleton. This study aims to stereoselectively synthesize the cis-fused 5,6-ring skeleton with two tetrasubstituted carbons at both angular positions using a model compound. The results revealed that the desymmetrization of the 2-methyl-1,3-cyclopentanedione moiety via the DL-proline-mediated intramolecular aldol reaction of a pentanal derivative bearing an isopropenyl group and the five-membered ring at the 3- and 5-position, respectively, provided the desired cis-fused skeleton. This reaction can construct four contiguous stereogenic centers of the bicyclic skeleton with the two angular positions in good yield with high stereoselectivity. Further, this reaction was applied to the kinetic resolution of the racemate using L-proline, providing the enantiomeric pure aldol product with the desired skeleton. This method can be utilized for total synthesis of picrotoxane-type sesquiterpenes.

Two series of 2-substituted benzimidazole conjugated 1,3,4-oxadiazole derivatives were designed, synthesized and evaluated for their cytotoxic activities against the three human cancer cell lines (cervical cancer (HeLa), breast cancer (MCF-7) and lung cancer (A549)). As the results 14 compounds demonstrated consistent to stronger cytotoxicities compared to the control 5-fluorouracil (5-FU) towards the tested cell lines including 4c (HeLa); 4b, 4e, 4h, 7i–j, 7m–n, 7s (MCF-7); 7b (MCF-7, A549); 7h (HeLa, MCF-7); and 4d, 4i, 7c (HeLa, MCF-7, A549), with the IC₅₀ ranging from 2.7 to 38 µM. Notably, compound 4b illustrated almost 5-fold activity against the MCF-7 while 4d, 4i were 9- and 8-fold (HeLa), 4.5- and 13-fold (MCF-7), 4.7- and 4-fold (A549) increase in activity compared to 5-FU, respectively, and were found as lead compounds. These findings suggest that compounds 4b, 4d and 4i merit further characterization and can serve as promising scaffolds in the discovery of new potent anticancer agents.

We prepared two kinds of fine particles by treating lactose monohydrate (Lac) with the same formulation in a fluidized-bed granulator, which differed in the spraying air pressure. Raman intensities of treated Lac during processing were measured using a handheld-type Raman spectrometer and plotted against particle size. As particle size increased, Raman intensity decreased in both operating conditions. A linear relationship between them was observed, and regression lines were obtained with good correlation coefficients as calibration curves in both operating conditions. We also prepared two other types of fine particles by treating Lac with the same formulation in a fluidized-bed granulator, which differed in the scale or processing mechanism. The particle size could be successfully predicted using the calibration curve obtained taking powder porosity into consideration. Based on this study, we present a new at-line approach in process analytical technology to monitor and predict particle size using a handheld-type Raman spectrometer.

Numerous efforts have been devoted to improving the solubility of poorly water-soluble drugs. Recently, it was reported that the use of metal-organic frameworks (MOFs), which are a new class of porous materials consisting of metal ions and organic ligands, is effective in improving the solubility of poorly water-soluble drugs. Our previous study demonstrated an improvement in the solubility of indomethacin (IDM) triggered by the zeolitic imidazolate framework-8 (ZIF-8). The present study aimed to elucidate the solubilization mechanism using the ZIF series, namely, ZIF-8, ZIF-67, and ZIF-L. It was confirmed that the solubility of ZIF-trapped IDM and ibuprofen (IBU) was enhanced compared to the raw drugs, regardless of the ZIF type. This study focused on 2-methylimidazole (2-MIM), which is commonly used as a ZIF organic ligand. Both IDM and IBU were easily dissolved by the addition of 2-MIM, suggesting that the presence of 2-MIM enhanced the solubility of the drugs. Inductively coupled plasma measurements also confirmed the presence of metal ions of ZIFs in the supernatant solution after the drug release tests, indicating the decomposition of ZIFs during drug release. The findings of this study demonstrated the solubilization mechanism of poorly water-soluble drugs using ZIF particles. We observed that the drugs loaded on the ZIFs were released simultaneously with the decomposition of some of the ZIFs. The 2-MIM molecules were also released concurrently. The presence of 2-MIM improved the solubility of poorly water-soluble drugs.

The highly enantioselective lipase-catalyzed kinetic resolution (KR) of racemic C₁-symmetric biaryl compounds including heterocyclic moieties, such as carbazole and dibenzofuran, has been achieved for the first time. This enzymatic esterification was accelerated by the addition of disodium carbonate while maintaining its high enantioselectivities, and was particularly effective for biaryls having N-substituted carbazole moieties. Furthermore, mesoporous silica-supported oxovanadium-catalyzed cross-dehydrogenative coupling of 3-hydroxycarbazole and 2-naphthol was followed by the lipase-catalyzed KR in one-pot to synthesize the optically active heterocyclic biaryl compounds with high optical purity.

It is mandatory to detect the powder cohesiveness of biopharmaceutical dry powder inhaler (Bio-DPI) formulations and their effect on their performance. Normally, Bio-DPI formulations consist of highly cohesive components with higher drug amounts than small molecules. Herein, a formulation study of a high-drug-ratio Bio-DPI was performed, detecting the risk of powder caking in DPI formulations. The Bio-DPI formulation was manufactured via the spray-dry method followed by mixing with excipients. Powder caking was detected through the void forming index (VFI), which was calculated using pressure drop measured by inverse gas chromatography (iGC). Since VFI can be used to evaluate the structural changes induced by powder caking over time with less than 1 g of sample, VFI is considered suitalbe to apply for DPI formulation screening. The risk of powder caking was detected in spray dryed particles at more than 45% relative humidity (RH) humidity condition, mannitol (as a carrier particle) and magnesium stearate (as a lubricant) were added to the formulations. With formulation screening, addition of more than 40% of mannitol was suggested to reduce the risk of powder caking. Selected DPI formulation remained higher emitted ratio (95.6%), than spray dried particle (52.5%) at 25 °C 65% RH condition for 1-month storage. In conclusion, VFI measurement is useful for selecting the DPI formulation by mitigating powder caking risk with limited samples.

Habiterpenol is a G2 checkpoint inhibitor isolated from the culture broth of Phytohabitans sp. 3787_5. Here, we report the synthesis of new habiterpenol analogs through the total synthesis process of habiterpenol and evaluating the analogs for G2 checkpoint inhibitory activity. We investigated two different synthetic approaches for total synthesis, with intramolecular conjugate addition and Ti(III)-mediated radical cyclization as key reactions. Although the former was unsuccessful, the latter reaction facilitated stereoselective total synthesis and determination of the absolute configuration of habiterpenol. The extension of these chemistries to a structure–activity relationship (SAR) study gave new habiterpenol analogs, which could not be derived from natural habiterpenol and only be synthesized by applying the total synthesis. Therefore, this study provides important insights into SAR studies of habiterpenol.

A novel alkaloid caulophyine A (1) was isolated from the roots of Caulophyllum robustum Maxim., along with six known alkaloids 2–7. The structure of 1 was elucidated by extensive NMR and high resolution-time-of-flight (HR-TOF)-MS analyses, it is a rare nitrogen containing polycyclic aromatic hydrocarbon. The in vitro bioassays revealed that 2 presented remarkable cytotoxicity against A549 with an IC₅₀ value of 3.83 µM in comparison with the positive control etoposide (IC₅₀ = 11.63 µM). Compounds 1 and 2 also displayed weak Acetylcholinesterase (AChE) inhibitory activity with IC₅₀ values of 123.03 and 80.74 µM respectively.

Prodrugs have seen increased clinical applications as therapeutic agents, as they reduce undesirable side effects and improve the therapeutic potential of drugs. While microorganisms produce numerous secondary metabolites with useful medicinal properties, there are only a handful of naturally occurring prodrugs discovered to date. The techniques of isolating secondary metabolites with therapeutic potential from natural product producers have been developed extensively over the years. However, the methods of identifying prodrugs from microbes have not been examined in depth, partly because prodrug-type compounds inherently lack the biological activities that are often used to screen for therapeutically useful secondary metabolites. Therefore, we hypothesized that the difficulty in searching for natural prodrug-type compounds may be addressed by simulating human prodrug activation within natural product-producing microbes. We chose to introduce human CYP (hCYP) into natural product-producing filamentous fungi, because hCYPs are the key enzymes that activate prodrugs in human body, and filamentous fungi are known to be prolific producers of a wide variety of natural products. Here, we successfully identified a cytotoxic, antibiotic and potential anti-diabetic natural product leporin B from Aspergillus flavus that was previously not known to produce this compound. Through bioinformatic and metabolite analyses, we identified the prodrug-equivalent compound leporin C that is converted into leporin B by the action of the hCYP isoenzyme 3A4. By employing various prodrug-activating enzymes and microbes that biosynthesize diverse arrays of natural products, we should be able to probe wider biosynthetic space for identification of interesting prodrug-type natural products.