Motofumi Miura

Palladium(II)-Catalyzed Enantioselective C(sp3)–H Activation Using a Chiral Hydroxamic Acid Ligand

An enantioselective method for Pd(II)-catalyzed cross-coupling of methylene β-C(sp3)–H bonds in cyclobutanecarboxylic acid derivatives with arylboron reagents is described. High yields and enantioselectivities were achieved through the development of chiral mono-N-protected α-amino-O-methylhydroxamic acid (MPAHA) ligands, which form a chiral complex with the Pd(II) center. This reaction provides an alternative approach to the enantioselective synthesis of cyclobutanecarboxylates containing α-chiral quaternary stereocenters. This new class of chiral catalysts also show promises for enantioselective β-C(sp3)–H activation of acyclic amides.

Chirality in dynamic supramolecular nanotubes induced by a chiral solvent.

Amplification of chirality has been reported in polymeric systems. It has also been shown that related effects can occur in polymer-like dynamic supramolecular aggregates, if a subtle balance between noncovalent interactions allows the coupling between a chiral information and a cooperative aggregation process. In this context, we report a strong majority-rules effect in the formation of chiral dynamic nanotubes from chiral bisurea monomers. Furthermore, similar helical nanotubes (with the same circular dichroism signature) can be obtained from racemic monomers in a chiral solvent. Competition experiments reveal the relative strength of the helical bias induced by the chiral monomer or by the chiral solvent. The nanotube handedness is imposed by the monomer chirality, whatever the solvent chirality. However, the chirality of the solvent has a significant effect on the degree of chiral induction.

Cucurbitane Triterpenoids from the Leaves of Momordica charantia, and Their Cancer Chemopreventive Effects and Cytotoxicities

Seventeen cucurbitane‐type triterpenoids, 1–17, including six new compounds, (23E)‐3β,25‐dihydroxy‐7β‐methoxycucurbita‐5,23‐dien‐19‐al (1), (23S*)‐3β‐hydroxy‐7β,23‐dimethoxycucurbita‐5,24‐dien‐19‐al (6), (23R*)‐23‐O‐methylmomordicine IV (7), (25ξ)‐26‐hydroxymomordicoside L (8), 25‐oxo‐27‐normomordicoside L (9), and 25‐O‐methylkaravilagenin D (12), were isolated from a MeOH extract of the leaves of Japanese Momordica charantia. The structures of new compounds were elucidated on the basis of extensive spectroscopic analyses and comparison with literature. Compounds 1–17 were examined for their inhibitory effects on EpsteinBarr virus early antigen (EBV‐EA) activation induced with 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells, a known primary screening test for inhibitors of tumor promotion. Four compounds, 1, (23E)‐3β,7β‐dihydroxy‐25‐methoxycucurbita‐5,23‐dien‐19‐al (2), karavilagenin D (11), and 12, showed potent inhibitory effects on EBV‐EA induction with IC50 values in the range of 242–264 mol ratio/32 pmol TPA. In addition, compounds 1 and 11 exhibited inhibitory effects on skin‐tumor promotion in an in vivo two‐stage mouse skin carcinogenesis test based on 7,12‐dimethylbenz[a]anthracene (DMBA) as initiator, and with TPA as a promoter. Furthermore, upon evaluation of the cytotoxic activities of compounds 1–17 against human cancer cell lines, compounds 2, 5–7, 9, and 14 showed potent activities against HL60 cell line, and compound 2 against SK‐BR‐3 cell line.

Asymmetric Synthesis of γ-Hydroxy α-Enones by 1,8-Diazabicyclo[5.4.0]undec-7-ene-Catalyzed Stereoselective Rearrangement of Chiral α-Sulfinyl Enones

The asymmetric rearrangement of optically active alpha-sulfinyl enone 1 induced by catalytic DBU and triphenylphosphine gave optically active gamma-hydroxy alpha-enone derivatives (up to 99% ee) in good yield following treatment with aqueous hydrogen peroxide.

In Vitro and in Vivo Anti-Influenza Virus Activity of Diarylheptanoids Isolated from Alpinia Officinarum

Background: Diarylheptanoids (AO-0002 [7-(4″-hydroxy-3″-methoxyphenyl)-1-phenyl-4E-hepten-3-one] and AO-0011 [(5S)-5-hydroxy-7-(4″-hydroxyphenyl)-1-phenyl-3-heptanone]) isolated from Alpinia officinarum have been reported to exhibit anti-influenza virus activity in vitro. Hence, efficacies against influenza virus infection and the mode of antiviral action were evaluated in vivo and in vitro, respectively. Methods: In a murine influenza virus infection model, diarylheptanoids were orally administered three times daily to mice infected with influenza A/PR/8/34 virus for 6 days after infection. AO-0002 was examined for its antiviral activity against the wild types of influenza viruses A/PR/8/34 (H1N1), oseltamivir-resistant A/PR/8/34 (H1N1), A/Bangkok/93/03 (H1N1), A/Ishikawa/7/82 (H3N2), A/Fukushima/13/43 (H3N2), B/Singapore/222/79 and B/Fukushima/15/93 in plaque reduction or yield reduction assays. The mode of anti-influenza virus action was assessed by a virus adsorption assay, immunofluorescence assay of viral antigens, and inhibition of viral messenger RNA synthesis using real-time reverse transcriptase PCR. Results: AO-0002 at 100 mg/kg was significantly effective in reducing the body weight loss and prolonging survival times of infected mice without toxicity, but AO-0011 was not. AO-0002 at 30 and 100 mg/kg significantly reduced virus titres in bronchoalveolar lavage fluids of the lungs on days 3 and 6 after infection. AO-0002 exhibited anti-influenza virus activity against all viruses used, including the oseltamivir-resistant strain in vitro. The compound had no effect on virus adsorption or invasion into cells, but dose-dependently suppressed the expression of viral messenger RNA and antigens. Conclusions: AO-0002 was suggested to have a different anti-influenza virus action to that of oseltamivir and was verified to show anti-influenza activity in vitro and in vivo.

Glycosidic Inhibitors of Melanogenesis from Leaves of Passiflora edulis

A new flavonoid glycoside, chrysin 6‐C‐β‐rutinoside (chrysin α‐L‐rhamnopyranosyl‐(1→6)‐C‐β‐glucopyranoside; 2), and two new triterpene glycosides, (31R)‐31‐O‐methylpassiflorine (7) and (31S)‐31‐O‐methylpassiflorine (8), along with 14 known glycosides, including three flavonoid glycosides, 1, 3, and 4, six triterpene glycosides, 5, 6, and 9–12, three cyano glycosides, 13–15, and two other glycosides, 16 and 17, were isolated from a MeOH extract of the leaves of Passiflora edulis (passion flower; Passifloraceae). The structures of new compounds were elucidated on the basis of extensive spectroscopic analysis and comparison with literature data. Upon evaluation of compounds 1–17 against the melanogenesis in the B16 melanoma cells induced with α‐melanocyte‐stimulating hormone (α‐MSH), three compounds, isoorientin (1), 2, and (6S,9R)‐roseoside (17), exhibited inhibitory effects with 37.3–47.2% reduction of melanin content with no, or almost no, toxicity to the cells (90.8–100.2% cell viability) at 100 μM. Western blot analysis showed that compound 2 reduced the protein levels of MITF, TRP‐1, and tyrosinase, in a concentration‐dependent manner while exerted almost no influence on the level of TRP‐2, suggesting that this compound inhibits melanogenesis on the α‐MSH‐stimulated B16 melanoma cells by, at least in part, inhibiting the expression of MITF, followed by decreasing the expression of TRP‐1 and tyrosinase. In addition, compounds 1–17 were evaluated for their inhibitory effects against the EpsteinBarr virus early antigen (EBV‐EA) activation induced by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) in Raji cells.

Stereochemically Controlled Asymmetric 1,2-Reduction of Enones Mediated by a Chiral Sulfoxide Moiety and a Lanthanum(III) Ion

Enantiomerically pure (Z)-β-sulfinyl allylic alcohols of either handedness can be readily prepared from (Z)-β-sulfinyl enones using NaBH(4) or DIBAL reductants in the presence of LaCl(3) as a chelating agent. A chiral sulfoxide auxiliary induces the remote 1,2-asymmetric reduction (1,4-induction) to afford various chiral allylic alcohols in high yields with excellent stereoselectivities (up to 100% de).

Antiviral activity of diarylheptanoid stereoisomers against respiratory syncytial virus in vitro and in vivo.

We previously showed that (5S)-5-hydroxy-7-(4-hydroxyphenyl)-1-phenylhept-3-one (AO-0011) and (5S)-5-methoxy-1,7-diphenylhept-3-one (AO-0016) isolated from Alpinia officinarum exhibited stronger anti-influenza virus activity and anti-respiratory syncytial virus (RSV) activity, respectively, than the other isolated diarylheptanoids. In this study, we synthesized an enantiomer (AO-0503) and racemate (AO-0504) of AO-0011 and an enantiomer (AO-0514) of AO-0016. The anti-RSV activities of the three stereoisomers (AO-0503, AO-0504, and AO-0514) and AO-0011 were examined in vitro and in vivo to evaluate the stereoisomeric effect on anti-RSV activity. In a plaque reduction assay using human epidermoid carcinoma cells, all four diarylheptanoids significantly exhibited anti-RSV activity, and AO-0514 and AO-0016 exhibited stronger anti-RSV activity than AO-0503, AO-0504, and AO-0011. In a murine RSV infection model, all four diarylheptanoids with anti-RSV activity in vitro were also significantly effective in reducing virus titers in the lungs of RSV-infected mice. In the histopathological analysis of RSV-infected lungs, the oral administration of even AO-0514, which showed the lowest reduction of virus titers in the lungs, was significantly effective in reducing the infiltration of lymphocytes and in reducing the interferon-γ level, which is a marker of severity of pneumonia due to RSV infection, in bronchoalveolar lavage fluids prepared from RSV-infected mice. Although the stereoisomeric effects of diarylheptanoids on anti-RSV activity varied moderately, all four diarylheptanoids examined were suggested to ameliorate pneumonia and have a potential anti-RSV activity in vivo. They are possibly mother compounds for the development of an anti-RSV drug in the future.

A novel metabolic activation associated with glutathione in dimethylmonothioarsinic acid (DMMTAV)-induced toxicity obtained from in vitro reaction of DMMTAV with glutathione

The purpose of the present study was to elucidate the metabolic processing of dimethylmonothioarsinic acid (DMMTA(V)), which is a metabolite of inorganic arsenic and has received a great deal of attention recently due to its high toxicity. The metabolites produced from an in vitro reaction with GSH were analyzed by high performance liquid chromatography-time of flight mass spectrometer (HPLC-TOFMS), HPLC with a photodiode array detector (PDA), and also gas chromatography-mass spectrometry (GC-MS) and GC with a flame photometric detector (FPD). The reaction of dimethylarsinic acid (DMA(V)) with GSH did not generate DMA(V)-SG but did generate dimethylarsinous acid (DMA(III)) or DMA(III)-SG. On the contrary, we confirmed that the reaction of DMMTA(V) with GSH directly produced the stable complex of DMMTA(V)-SG without reduction through a trivalent dimethylated arsenic such as DMA(III) and DMA(III)-SG. Furthermore, the present study suggests the production of hydrogen sulfide (H2S) and dimethylmercaptoarsine (DMA(III)-SH), a trivalent dimethylated arsenic, as well as DMA(III) and DMA(III)-SG in the decomposition process of DMMTA(V)-SG. These results indicate that the toxicity of DMMTA(V) depends not only on the formation of DMA(III) but also on at least those of H2S and DMA(III)-SH.

Isolation and structural identification of a direct-acting mutagen derived from N-nitroso-N-methylpentylamine and Fenton’s reagent with copper ion

N-Nitrosodialkylamines show their mutagenicity by forming α-hydroxynitrosamines in the presence of rat S9 mix in the Ames assay. The hydroxyl radical derived from Fe(2+)-H(2)O(2) (Fentons reagent) with Cu(2+) activates N-nitrosamines, with an alkyl chain longer than a propyl constituent, to a direct-acting mutagen. The reactivity of Fe(2+)-Cu(2+)-H(2)O(2) on nitrosamines in relation to their metabolic activation is not fully characterized. Here, we report the identification of the direct-acting mutagen derived from N-nitroso-N-methylpentylamine (NMPe) in the presence of Fe(2+), Cu(2+), H(2)O(2) and nitric oxide (NO), which is a product of nitrosamine metabolism. A dichloromethane extract of the NMPe reaction mixtures was fractionated by silica gel column chromatography several times and by a preparative high performance liquid chromatography (HPLC); we obtained white crystals as a product. The direct-acting mutagen that was isolated was provisionally identified as 5-ethyl-5-nitro-1-pyrazoline 1-oxide by (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy and X-ray crystallography. To confirm the structure of the mutagen, the authentic compound was synthesized from 2-nitrobutene and diazomethane, followed by N-oxidation with m-chloroperoxybenzoic acid. The (1)H NMR spectral data from the direct-acting mutagen that was synthesized was identical to the data from the isolated mutagen. Furthermore, the authentic 5-ethyl-5-nitro-1-pyrazoline 1-oxide was mutagenic in Salmonella typhimurium TA1535. The results showed that 5-ethyl-5-nitro-1-pyrazoline 1-oxide was a direct-acting mutagen derived from the reaction of NMPe and Fe(2+)-Cu(2+)-H(2)O(2)-NO.