Published papers

A serious concern of doxorubicin (DOX) therapy is that it causes severe adverse effects, particularly cardiotoxicity. Carbon monoxide (CO) possesses powerful cytoprotective effects against drug-induced organ injury and is expected to ameliorate DOX-induced cardiotoxicity. In this study, a dual carrier of DOX and CO (CO-HemoAct-DOX) was fabricated based on a haemoglobin-albumin cluster (HemoAct), which is a protein cluster with a haemoglobin core structure wrapped by serum albumin. CO-HemoAct-DOX was synthesised by binding CO to a haemoglobin core and covalently conjugating (6-maleimidocaproyl)hydrazone derivative of DOX to an albumin shell. The average DOX/cluster ratio was about 2.6. In the in vitro cytotoxicity assay against cancer cells, the anti-tumour activity of CO-HemoAct-DOX was 10-fold lower than that of DOX in a 2D-cultured model, whereas CO-HemoAct-DOX suppressed the growth of tumour spheroids to the same extent as DOX in the 3D-cultured model. In colon-26 tumour-bearing mice, CO-HemoAct-DOX achieved DOX delivery to the tumour site and alleviated tumour growth more effectively than DOX. Furthermore, CO-HemoAct attenuated DOX-induced cardiomyocyte atrophy in H9c2 cells and elevated the levels of cardiac biomarkers in mice exposed to DOX. These results suggest that the dual delivery of CO and DOX using HemoAct is a promising strategy as an anti-tumour agent to realise well-tolerated cancer therapy with minimal cardiotoxicity.

The synthesis of 2,2-difluoro-1,4-diazaboroles was achieved through the condensation of aliphatic acyltrifluoroborates and amino-N-heteroarenes under acidic conditions. Various N-heteroarenes, including pyridine, pyrimidine, pyridazine, thiazole, and isoquinoline, were successfully employed in the reaction. Among the synthesized 2,2-difluoro-1,4-diazaboroles, the one with an isoquinoline structure exhibited the most intense light blue emission.

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Mankind has been searching for anticancer drugs from nature and artificial compounds. Since the discovery of englerin A, a guaiane sesquiterpene possessing the characteristic tricyclic 5–6-5 fused ring framework with contiguous seven stereogenic centers and isolated from Phyllanthus engleri, many synthetic groups have enthusiastically launched and accomplished its the chemical synthesis. All the synthetic groups focused on how to efficiently construct the tricyclic framework containing oxygen bridge with various approaches. In this review, the total and formal syntheses of englerin A reported to date are summarized.

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 3′,4′,7-Trimethoxyflavone (TMF) has been reported to show a potent reversal effect on drug resistance mediated by breast cancer resistance protein (BCRP)/ATP-binding cassette subfamily G member 2 (ABCG2). In this study, we designed and synthesized five derivatives with either a hydroxy group or a fluorine atom at C-5 and several kinds of capping moiety at the C-7 hydroxy group, on the same 3′,4′-dimethoxy-substituted flavone skeleton. We subsequently evaluated the efficacies of these compounds against BCRP-expressing human leukaemia K562/BCRP cells. Reversal of drug resistance was expressed as the concentration of compound causing a twofold reduction in drug sensitivity (RI 50 ). Of the synthesized compounds, the reversal effect of 5-hydroxy-3′,4′,7-trimethoxyflavone (HTMF, RI 50 7.2 nm) towards 7-ethyl-10-hydroxycamptothecin (SN-38) was stronger than that of TMF (RI 50 18 nm). Fluoro-substituted 5-fluoro-3′,4′,7-trimethoxyflavone (FTMF, RI 50 25 nm) and monoglycosylated 7-(β-glucosyloxy)-5-hydroxy-3′,4′-dimethoxyflavone (GOHDMF, 91 nm) also exhibited reversal effects, whereas the di- and triglycoside derivatives did not. TMF, HTMF and FTMF at 0.01–10 μm upregulated the K562/BCRP cellular accumulation of Hoechst 33342 nuclear staining dye. In addition, western blotting revealed that treatment of K562/BCRP cells with 0.1 μm TMF, HTMF or FTMT suppressed the expression of BCRP. HTMF showed the strongest inhibition of BCRP-mediated efflux and suppression of BCRP expression of the three effective synthesized flavones.

© 2019 American Chemical Society. Small and simple bioorthogonal reactive handles that can be readily encoded by natural processes are important for bioconjugation. A rapid nickel-promoted N-H arylation of pyroglutamate-histidine sequences with 2-nitroarylboronic acids proceeds under mild aqueous conditions. Chemoselective activation of a lactam amide N-H within a peptide or protein provides a new approach to selective conjugation in polyamide structures.

© 2020 Wiley-VCH GmbH Interconversion of atropisomers of chiral 3,3’-di-tert-butyl-9,9’-bicarbazole linked by a single N−N bond was analyzed by DFT calculations and experiments. The calculations revealed that the trans transition state has a lower energy for the interconversion than the cis transition state. The lowest transition state of interconversion between natural dixiamycins A and B containing a 9,9’-bicarbazole structure was found to be the trans transition state. The calculations also indicated that degradation through N−N bond cleavage was faster than racemization. Atropisomeric enantiomers of 3,3’-di-tert-butyl-9,9’-bicarbazole were resolved by chiral HPLC for the first time, and then racemization and N−N bond cleavage were investigated by heating experiments, showing that racemization did not take place below the degradation temperature.

© 2020 The Japan Institute of Heterocyclic Chemistry. The syntheses of indirubin (76% yield), 6-bromoindirubin (82% yield), and 6-bromoindirubin-3′-oxime (78% yield in two steps) were achieved via the lipase-triggered aldol condensation between isatins and an indoxyl anion in tetrahydrofuran under anhydrous and anaerobic conditions as the key step. The aldol donor was generated in situ by Burkholderia cepacia lipase (Amano PS-IM)-catalyzed deacetylation of commercially available and stable indoxyl acetate in the presence of triethylamine and with 2-propanol as the transesterification reagent. The scale-up of the presently developed reactions is easier than that in the previously reported chemical aldol condensations, because of the simplicity of the isolation procedure and suppression of the oxidative byproduct formation from indoxyl acetate.

© 2019 Elsevier B.V. Linezolid (LZD) is a widely used antimicrobial that is active against a broad range of disease-causing bacteria. Myelosuppression is major treatment-limiting toxicity of LZD that occurs more frequently in patients with renal insufficiency. Quantification of LZD and its two primary metabolites (PNU-142300 and PNU-142586), which undergo significant renal elimination, may support design of improved dosing strategies to mitigate the risk of myelosuppression. In this study, we established the first liquid chromatography-tandem mass spectrometry (LC–MS/MS) method for the simultaneous quantification of LZD and its main metabolites in human serum. Proteins in serum samples were precipitated with acetonitrile containing a deuterated internal standard. Chromatographic separation of analytes was performed with Waters X-bridge column (C18, 150 × 4.6 mm, 3.5 μm) at 25 °C and subjected to mass analysis using positive electro-spray ionization. The mobile phase A was water with 0.1% formic acid, and mobile phase B was acetonitrile with 0.1% formic acid at a flow rate of 0.6 mL/min, within a 15 min run time. Standard curves were linear and correlation coefficients (r2) were ≥0.99 for concentration ranges of 0.1–50 μg/mL for LZD and PNU-142300, and 0.1–25 μg/mL for PNU-142586. The inter- and intra-assay precisions were <15% for all analytes in quality control samples, and the accuracies ranged from 97 to 112%. Extraction recoveries ranged from 78 to 103% for all analytes, and there was no significant matrix effect. Samples from 10 patients (5 with renal impairment) were assayed. Mean (SD) LZD, PNU-142300 and PNU-142586 trough concentrations were 19.4(6.8), 11.6(6.8), 25.7(16.4) μg/mL, respectively, in patients with renal impairment. These values were 2.5-, 5.8-, and 6.8-fold higher for LZD, PNU-142300 and PNU-142586, respectively compared to patients without renal impairment. The method was effectively applied in the determination of LZD and its main metabolites in human serum.

This journal is © The Royal Society of Chemistry. A stepwise dehydrogenative cross-coupling method was developed for the formation of sterically hindered Csp3-Csp3 bonds. Intramolecular dehydrogenative O-alkylation of a β-ketoester by 2,3-dichloro-5,6-dicyano-p-benzoquinone to form an oxolane followed by Lewis acid-catalyzed [1,3]-rearrangement furnished the sesquiterpene arylmethylcyclopentane skeleton. The formal syntheses of herbertane-type β-herbertenol, cuparane-type enokipodins A and B were also achieved.

© 2020, © 2020 Japan Society for Bioscience, Biotechnology, and Agrochemistry. Hot water extraction of D-arabinofuranosylvitexin from the raw leaves of commercially available Basella alba “Tsurumurasaki” and subsequent acidic hydrolysis was improved to be a procedure using a high-pressure steam sterilizer to afford vitexin. The amount was estimated to be 14.1 mg from 1 g of dry weight of the raw leaves, whose recovery was calculated to be 95% based on the estimated content of D-arabinofuranosylvitexin in B. alba raw leaves. The product was dehydratively cyclized between hydroxy groups on the carbohydrate and flavone skeletons under modified Mitsunobu reaction conditions in N,N-dimethylformamide to give chafuroside B, which is known to be a bioactive Oolong tea polyphenol. Through these transformations, 10.2 mg of chafuroside B could be semisynthesized from 1 g of dry weight of the raw leaves, and the efficiency was improved compared to that from the extraction from Oolong tea (3.4 μg from 1 g of dry weight).

© 2020, © 2020 Japan Society for Bioscience, Biotechnology, and Agrochemistry. Catathelasmols C, D, and E, which had been isolated from Catathelasma imperiale as inhibitors for 11-hydroxysteroid dehydrogenases, were comprehensively semisynthesized from commercially available D-glutamic acid. The key synthetic intermediate, (R)-pentane-1,2,5-triol, was site-selectively acetylated by treatment with vinyl acetate and Candida antarctica lipase B (Novozym 435) in tetrahydrofuran (THF) at 25°C to furnish 1,5-diacetate (catathelasmol E, quantitative). The acetylation occurred site-selectively on the primary alcohols at the C-1 and C-5 positions over the secondary alcohol at the C-2 position. Dichromic acid oxidation provided 2-oxopentane-1,5-diyl diacetate (catathelasmol C, 78%). Burkholderia cepacia lipase-catalyzed transesterification with methanol in THF at–5°C proceeded preferentially on the acetate at C-1 located adjacent to the C-2 carbonyl group over the other terminal acetate at the C-5 position. 5-Hydroxy-4-oxopentyl acetate (catathelasmol D) was obtained in 53% yield.

© 2020 American Society for Microbiology. All Rights Reserved. In patients with renal impairment (n=22 of 39), the median serum concentrations of linezolid, PNU-142300, and PNU-142586 were 1.6-, 3.3-, 2.8-fold higher, respectively, than in patients without renal impairment. Metabolite concentrations in paired samples were poorly correlated with linezolid concentrations (r2 = 0.26 for PNU-142300 and 0.06 for PNU-142586). Linezolid and its metabolites share potential toxicophores that deserve characterization to mitigate higher myelosuppression risk in patients with renal impairment.

© The Royal Society of Chemistry 2020. Polypeptides present remarkable selectivity challenges for chemical methods. Amino groups are ubiquitous in polypeptide structure, yet few paradigms exist for reactivity and selectivity in arylation of amine groups. This communication describes the utilization of boronic acid reagents bearing certaino-electron withdrawing groups for copper-mediated amine arylation of the N-terminus under mild conditions and primarily aqueous solvent. The method adds to the toolkit of boronic acid reagents for polypeptide modification under mild conditions in water that shows complete selectivity for the N-terminus in the presence of lysine side chains.

Tissue engineering and cell transplantation therapy have become promising therapies for intractable diseases. These approaches require cell separation technology without cell modification. Accordingly, in this study, we developed a novel cell separation method using a thermoresponsive block copolymer brush with an affinity peptide. A block copolymer brush with bottom poly(2-hydroxyethyl methacrylate [HEMA]-co-propargyl acrylate) and top poly(N-isopropylacrylamide-co-HEMA) segments was prepared through two steps of atom transfer radical polymerization. Then, cell affinity peptides were conjugated to the bottom segment of the copolymer brush through a click reaction. Using cRGD as a cell-Affinity peptide, enhancement of cell adhesion with rapid adhesion on the copolymer brush was observed at 37 °C, whereas the copolymer brush without cRGD did not exhibit cell adhesion. Temperature-modulated cell adhesion and detachment were performed with a relatively long upper segment because the affinity between peptides and cells was modulated by the swelling and shrinking of the upper thermoresponsive segment. Selective endothelial cell adhesion was performed at 37 °C using GGGREDV as an affinity peptide. Smooth muscle cells and fibroblasts did not adhere to the copolymer brush. Adhered human umbilical vein endothelial cells (HUVECs) were successfully recovered by reducing the temperature to 20 °C. Based on the properties of the copolymer brush, HUVECs could be purified using a mixture of cells simply by changing the temperature. These results demonstrated that the prepared copolymer brush with cell affinity peptides could be a useful cell separation tool because the cells could be separated with specificity and without cell modification using a simple procedure.

Construction of the hydroquinoline skeleton of symbioimine by Cu-mediated N-alkenylation or O-alkenylation of an allyl aminoalcohol, in which either chemoselectivity could lead to the target compound, was investigated. O-alkenylation followed by Claisen rearrangement was favored with high selectivity under a ligand-free condition. Subsequent intramolecular condensation furnished the hydroquinoline skeleton of symbioimine.

We developed an intramolecular cyclization of m-homoprenylphenols and related m-prenylphenols to bicyclic skeletons by hypervalent iodine reagents through an oxidative nucleophilic aromatic substitution using the prenyl group as a carbon nucleophile. The reaction was applicable for the syntheses of 5/6-, 6/6-, and 7/6-fused ring systems.

The 1,2-rearrangement of o-quinols has been a long-standing unsolved problem since 1958. Although the rearrangement is expected to be useful for syntheses of catechol derivatives, it is hampered by many competing reactions and has not been developed as a useful methodology. Here, we succeeded in settling this problem by a first systematic thorough investigation, establishing the 1,2-rearrangement as a cascade reaction with a retro Diels-Alder reaction from o-quinol dimers. This is a useful strategy for syntheses of substituted catechols used as synthetic building blocks for bioactive compounds and material molecules. o-Quinol dimers were synthesized by improved oxidative hydroxylation of substituted phenols followed by spontaneous Diels-Alder reaction. The dimers then underwent the retro Diels-Alder reaction to regenerate the o-quinols followed by 1,2-rearrangement under neutral heating conditions at an appropriate temperature depending on the migratory substituent, furnishing substituted catechols in good yields. The competing reactions such as an elimination of a substituent or α-ketol rearrangement were minimized by controlling the reaction temperature.

The 1H-2-benzopyran-5,8-dione structure was synthesized by a cascade reaction through Michael addition, elimination of HBr, and O-alkylation between a dibromobenzoquinone derivative and β-ketoesters under basic conditions. The reaction using potassium carbonate and 18-crown-6 in THF was the best condition, giving 1H-2-benzopyran-5,8-dione derivatives in good yields. The UV-vis absorption spectrum and cyclic voltammogram of the synthesized 1H-2-benzopyran-5,8-dione derivative were measured, clarifying the photophysical and redox properties.

© 2018 Japan society for Bioscience, Biotechnology, and Agrochemistry. Fisetin and 2′,4′,6′-trihydroxydihyrochalcone 4′-O-β-neohesperidoside were synthesized from commercially available quercetin and naringin in five steps. The key steps are site-selective deacetylation and subsequent deoxygenation. The target molecules were obtained in 37% and 23% yields from the starting materials, respectively.

© 2018 Japan Society for Bioscience, Biotechnology, and Agrochemistry Trilobatin [4-(β-D-glucopyranosyloxy)-2,4”,6-trihydroxydihydrochalcone] was synthesized from commercially available naringin in three steps with an overall yield of 30%. The key step was the acid-catalyzed site-selective hydrolysis of terminal α-rhamnopyranosidic linkage in neohesperidose involved in naringin under controlled conditions, by applying a high-pressure steam sterilizer.