Convergent Synthesis of the <i>ent</i>-ZA′B′C′D′-Ring System of Maitotoxin

Stereoselective synthesis of the <i>ent</i>-ZA′B′C′D′-ring system of maitotoxin has been accomplished through a convergent strategy utilizing Suzuki–Miyaura cross coupling reaction of ZA′-ring alkylborane and C′D′-ring (<i>Z</i>)-vinyl iodide, and subsequent construction of the B′-ring by reduction of the <i>O</i>,<i>S</i>-acetal

Total Synthesis of Kehokorins A–E, Cytotoxic <i>p</i>‑Terphenyls

This paper describes a general method for the synthesis of kehokorins A–E, novel cytotoxic <i>p</i>-terphenyls. 2,4,6-Trihydroxybenzaldehyde served as a common building block for preparation of the central aromatic ring. Construction of their <i>p</i>-terphenyl skeletons was achieved by a stepwise Suzuki–Miyaura coupling, whereas the phenyldibenzofuran moiety was built up by an intramolecular Ullmann reaction. Introduction of an l-rhamnose residue into partly protected kehokorin B was performed by the trichloroacetimidate method

Production of Kinanthraquinone D with Antimalarial Activity by Heterologous Gene Expression and Biotransformation in Streptomyces lividans TK23

Two new compounds, kinanthraquinone C (1) and kinanthraquinone D (2), were isolated along with two known compounds, kinanthraquinone (3) and kinanthraquinone B (4), produced by the heterologous expression of the kiq biosynthetic gene cluster and its pathway-specific regulator, kiqA, in Streptomyces lividans TK23. The chemical structures of compounds 1 and 2 were determined using mass spectrometry and nuclear magnetic resonance analyses. To examine a biosynthetic pathway of compounds 1 and 2, incubation experiments were conducted using S. lividans TK23 to supply the compounds 3 and 4. These experiments indicated that compounds 3 and 4 were converted to compounds 2 and 1, respectively, by the endogenous enzymes of S. lividans TK23. Compounds 2, 3, and 4 had antimalarial activities at half-maximal inhibitory concentration values of 0.91, 1.2, and 15 μM, respectively, without cytotoxicity up to 30 μM

Scandium-Catalyzed Syndiospecific Chain-Transfer Polymerization of Styrene Using Anisoles as a Chain Transfer Agent

The polymerization of styrene in the presence of various anisole derivatives has been examined by using the half-sandwich scandium diamino­benzyl complex (C₅Me₄SiMe₃)­Sc­(CH₂C₆H₄NMe₂-<i>o</i>)₂ with borate [Ph₃C]­[B­(C₆F₅)₄]. The syndiospecific chain transfer polymerization of styrene proceeded efficiently via the <i>ortho</i>-C–H bond activation of anisoles, affording the corresponding end-<i>ortho</i>-anisyl-functionalized syndiotactic polystyrenes. The molecular weight of the resulting polymers could be controlled in a wide range by changing the styrene/anisole feeding ratio. Propenyl and halogen (F, Cl, Br, and I) substituents on the anisole compounds are compatible with the present catalyst system, thus enabling easy introduction of unsaturated CC double bond or halogen moieties together with the anisole functionality to the chain end of syndiotactic polystyrene

Synthesis of 3-phenyldibenzo[<i>b,d</i>]furan-type bioprobes utilizing vialinin B as a structural motif

<p>Vialinin B is a natural 3-phenyldibenzo[<i>b,d</i>]furan product with a powerful inhibitory activity against tumor necrosis factor (TNF)–α production. This article describes the synthesis of three types of biotinylated <i>p</i>-terphenyls designed for clarifying the target molecule of vialinin B. Construction of the carbon backbone of the core was accomplished by stepwise Suzuki–Miyaura coupling while the phenyl dibenzofuran moiety was built up by the Ullmann reaction. The biotinyl unit was attached through click chemistry.</p

Synthesis and Structural Revision of a Brominated Sesquiterpenoid, Aldingenin C

This paper describes a short step synthesis of the proposed structure for aldingenin C from <i>trans</i>-limonene oxide. The tetrahydropyran-fused 2-oxabicyclo[3.2.2]­nonane skeleton as the structural feature was constructed by an intramolecular epoxide-opening reaction and a brominative cyclization. The spectral data of the synthetic compound did not match those of the natural product reported. Re-examination of the reported NMR data using new CAST/CNMR Structure Elucidator suggests that the structure of aldingenin C should be revised to that of known caespitol

Flavimycins A and B, Dimeric 1,3-Dihydroisobenzofurans with Peptide Deformylase Inhibitory Activity from <i>Aspergillus flavipes</i>

Flavimycins A (<b>1</b>) and B (<b>2</b>), novel dimeric 1,3-dihydroisobenzofurans, were isolated as inhibitors of peptide deformylase from cultures of <i>Aspergillus flavipes</i>. Their chemical structures were established by NMR and MS data analysis. Compounds <b>1</b> and <b>2</b> exist as epimeric mixtures at C-1 through fast hemiacetal–aldehyde tautomerism. Compounds <b>1</b> and <b>2</b> inhibited <i>Staphylococcus aureus</i> peptide deformylase with IC₅₀ values of 35.8 and 100.1 μM, respectively. Consistent with their PDF inhibition, <b>1</b> showed two times stronger antibacterial activity than <b>2</b> on <i>S. aureus</i> including MRSA, with MIC values of 32–64 μg/mL

<i>N</i>¹, <i>N</i>¹⁴-diferuloylspermine as an antioxidative phytochemical contained in leaves of <i>Cardamine fauriei</i>

<p>Most Brassicaceae vegetables are ideal dietary sources of antioxidants beneficial for human health. <i>Cardamine fauriei</i> (Ezo-wasabi in Japanese) is a wild, edible Brassicaceae herb native to Hokkaido, Japan. To clarify the main antioxidative phytochemical, an 80% methanol extraction from the leaves was fractionated with Diaion® HP-20, Sephadex® LH-20, and Sep-Pak® C18 cartridges, and the fraction with strong antioxidant activity depending on DPPH method was purified by HPLC. Based on the analyses using HRESIMS and MS/MS, the compound might be <i>N</i>¹, <i>N</i>¹⁴-diferuloylspermine. This rare phenol compound was chemically synthesized, whose data on HPLC, MS and ¹H NMR were compared with those of naturally derived compound from <i>C. fauriei</i>. All results indicated they were the same compound. The radical-scavenging properties of diferuloylspermine were evaluated by ORAC and ESR spin trapping methods, with the diferuloylspermine showing high scavenging activities of the ROO^·, O₂^·−, and HO^· radicals as was those of conventional antioxidants.</p

Kinetically Controlled One-Pot Formation of DEFGH-Rings of Type B Physalins through Domino-Type Transformations

The characteristic DEFGH-ring system of type B physalins has been synthesized by means of a one-pot procedure incorporating domino-type ring transformations. Unexpectedly, we found that introduction of an α-hydroxyester functionality at C17 in ring E allowed the key 7-<i>endo</i> oxy-Michael reaction to proceed. Originally this was thought to be an unfavored process. This afforded the desired caged ring system to be formed in a kinetically controlled manner. Consecutive treatment with AcOH at 100 °C furnished the DEFGH-ring system in one pot

Hitoyol A and B, Two Norsesquiterpenoids from the Basidiomycete <i>Coprinopsis cinerea</i>

Hitoyol A (<b>1</b>), an unprecedented norsesquiterpenoid with an <i>exo</i>-tricyclo­[5.2.1.0^2,6]­decane skeleton, was isolated from the culture broth of Basidiomycete <i>Coprinopsis cinerea</i> along with a novel skeletal hitoyol B (<b>2</b>) containing 4-cyclopentene-1,3-dione. Their structures and absolute configurations were analyzed by single-crystal X-ray diffraction and electronic circular dichroism spectroscopic methods. Compound <b>1</b> is possibly biosynthesized through decarboxylation-induced cyclization of lagopodin B, a known cuparene-type sesquiterpenoid. Compound <b>2</b> showed weak antimalarial activity with an IC₅₀ of 59 μM