Total Synthesis of Clostrienose.

This paper considers the total synthesis of a cellular differentiation regulator of Clostridium acetobutylicum, clostrienose, which is a unique fatty-acid glycosyl ester consisting of clostrienoic acid, (3R,5E,8E,10E)-3-hydroxy-tetradeca-5,8,10-trienoic acid and α-d-galactofuranosyl-(1 → 2)-α-l-rhamnose. The key features of our synthesis include stereoselective construction of a skipped-triene system in clostrienoic acid and its esterification with a disaccharide residue. The partially protected clostrienoic acid employed for the coupling also served for the preparation of l-rhamnosyl clostrienoate, thus leading to confirmation of the proposed structure unambiguously.

Identification of a New Pyrrolyl Pyridoindole Alkaloid, Melpyrrole, and Flazin from Honey and Their Cough-Suppressing Effect in Guinea Pigs.

The cough-suppressing effect of honey was demonstrated for the first time using a guinea pig model whereby cough was induced by citric acid and capsaicin, and a new pyrrolyl pyridoindole, 1-(5-(hydroxymethyl)-1H-pyrrol-2-yl)-9H-pyrido[3,4-b]indole-3-carboxylic acid (1), named melpyrrole, and flazin (2) were identified as the active principle components. The structures of 1 and 2 were estimated using a combination approach of an activity-guided survey and LC-MS/MS multivariate analysis and were finally established by total synthesis of 1 and comparison with an authentic standard for 2. Both compounds showed antitussive activity comparable to that of dextromethorphan in guinea pigs. Their antitussive effects were unaffected by an opioid antagonist and reversed by a nitric oxide (NO) synthase inhibitor, indicating that these natural products do not act directly on opiate receptors but through the NO signaling pathway.

Total Synthesis of the Proposed Structure for Chaunopyran A and Its Absolute Configuration.

This paper describes a seven-step synthesis of the proposed structure for chaunopyran A produced by cocultivation of a Chaunopycnis sp. and Trichoderma hamatum. This synthesis included a coupling of a diene sulfone and a tetrahydropyranyl aldehyde as a key step. The sign of the specific rotation value of the synthetic sample was opposite that of the natural product, suggesting that the absolute configuration of the natural product should be revised.

Structural Studies on Stilbene Oligomers Isolated from the Seeds of Melinjo (Gnetum gnemon L.).

This paper describes the isolation and structural determination of a new stilbene dimer, named 7a-epi-gnetin C, from melinjo (Gnetum gnemon L.) seed extract. The relative structure was elucidated based on NMR spectroscopic evidence, while the absolute configuration was assigned by a combination of NMR and electronic circular dichroism spectroscopic analysis and chemical conversion. 7a-epi-Gnetin C was evaluated as an antioxidant and was shown to have a comparable activity to the known stilbene oligomers. In addition, the structural revision of gnetin L, a known stilbene dimer, was also discussed.

Isolation, Identification, and Synthesis of a New Prenylated Cinnamic Acid Derivative from Brazilian Green Propolis and Simultaneous Quantification of Bioactive Components by LC-MS/MS.

A new cinnamic acid derivative, (E)-3-[4-hydroxy-3-((E)-3-formyl-2-butenyl)phenyl]-2- propenoic acid (20) has been isolated from the ethanol extract of Brazilian green propolis along with three known cinnamic acid derivatives, 3,4-dihydroxy-5-prenyl-(E)-cinnamic acid (4), capillartemisin A (6), and 2,2-dimethylchromene-6-(E)-propenoic acid (8), and a flavonoid, dihydrokaempferide (16) by liquid-liquid participation, a series of column chromatography and preparative HPLC. Their structures have been determined by spectroscopic analyses and chemical synthesis of compound 20. The simultaneous quantification of 20 constituents, including 10 cinnamic acid derivatives, 7 flavonoids, and 3 caffeoylquinic acid derivatives, has also been developed and validated using LC-MS/MS. The new compound 20 was shown to activate PPAR α but not PPAR ß or γ.

Synthesis of polyozellin, a prolyl oligopeptidase inhibitor, and its structural revision.

Polyozellin is a p-terphenyl compound which was isolated from Polyozellus multiplex, and exhibits an inhibitory activity against prolyl oligopeptidase (POP). Its structure was assigned as 1 having a p-terphenyl skeleton including a p-substituted dibenzofuran moiety by spectroscopic analyses and chemical means. This paper describes the total syntheses of the proposed structure 1 for polyozellin and its o-isomer 2, revising the structure of polyozellin to the latter. These syntheses involved a double Suzuki-Miyaura coupling using chlorophenylboronic acid as a common key building block, and Cu mediated Ullmann cyclization as key steps. The inhibitory activities of synthetic compounds against POP and cancer cells were also evaluated.

Ca2+-Signal Transduction Inhibitors, Kujiol A and Kujigamberol B, Isolated from Kuji Amber Using a Mutant Yeast.

A podocarpatriene and a labdatriene derivative, named kujiol A [13-methyl-8,11,13-podocarpatrien-19-ol (1)] and kujigamberol B [15,20-dinor-5,7,9-labdatrien-13-ol (2)], respectively, were isolated from Kuji amber through detection with the aid of their growth-restoring activity against a mutant yeast strain ( zds1Δ erg3Δ pdr1Δ pdr3Δ), which is known to be hypersensitive with respect to Ca2+-signal transduction. The structures were elucidated by spectroscopic data analysis. Compounds 1 and 2 are rare organic compounds from Late Cretaceous amber, and the mutant yeast used seems useful for elucidating a variety of new compounds from Kuji amber specimens, produced before the K-Pg boundary.

Total Synthesis of Kehokorins A-E, Cytotoxic p-Terphenyls.

This paper describes a general method for the synthesis of kehokorins A-E, novel cytotoxic p-terphenyls. 2,4,6-Trihydroxybenzaldehyde served as a common building block for preparation of the central aromatic ring. Construction of their p-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.

Total Synthesis of the Proposed Structure for Aromin and Its Structural Revision.

This paper describes the first total synthesis of the proposed structure for aromin, an annonaceous acetogenin possessing an unusual bis-THF ring system, and its 4S,7R-isomer. The key steps involve an oxidative cyclization of a couple of terminal-diene alcohols and an intermolecular metathesis of an alkenyl tetrahydrofuran with an enone carrying a tetrahydrofuranyl lactone. The spectral data of both samples did not match those of aromin. Re-examination of the NMR data using the CAST/CNMR Structure Elucidator and chemical derivations suggested that the real structure of aromin should be revised to be a tetrahydropyran acetogenin, montanacin D. Cytotoxicities in human solid tumor cell lines for synthetic samples were also evaluated.

Isolation of Coralmycins A and B, Potent Anti-Gram Negative Compounds from the Myxobacteria Corallococcus coralloides M23.

Two new potent anti-Gram negative compounds, coralmycins A (1) and B (2), were isolated from cultures of the myxobacteria Corallococcus coralloides M23, together with another derivative (3) that was identified as the very recently reported cystobactamid 919-2. Their structures including the relative stereochemistry were elucidated by interpretation of spectroscopic, optical rotation, and CD data. The relative stereochemistry of 3 was revised to "S*R*" by NMR analysis. The antibacterial activity of 1 was most potent against Gram-negative pathogens, including Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumanii, and Klebsiella pneumoniae, with MICs of 0.1-4 µg/mL; these MICs were 4-10 and 40-100 times stronger than the antibacterial activities of 3 and 2, respectively. Thus, these data indicated that the ß-methoxyasparagine unit and the hydroxy group of the benzoic acid unit were critical for antibacterial activity.

Cytoprotective Effects of Lysophospholipids from Sea Cucumber Holothuria atra.

Lysophospholipids are important signaling molecules in animals and metazoan cells. They are widely distributed among marine invertebrates, where their physiological roles are unknown. Sea cucumbers produce unique lysophospholipids. In this study, two lysophospholipids were detected in Holothuria atra for the first time, lyso-platelet activating factor and lysophosphatidylcholine, with nuclear magnetic resonance and liquid chromatography-time-of-flight mass spectrometric analyses. The lipid fraction of H. atra contained lyso-platelet activating factor and lysophosphatidylcholine, and inhibited H2O2-induced apoptosis in the macrophage cell line J774A.1. The antioxidant activity of the lysophospholipid-containing lipid fraction of H. atra was confirmed with the oxygen radical absorbance capacity method. Our results suggest that the lysophospholipids from H. atra are potential therapeutic agents for the inflammation induced by oxidative stress.

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 trans-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.

Structural revision of kynapcin-12 by total synthesis, and inhibitory activities against prolyl oligopeptidase and cancer cells.

Kynapcin-12 is a prolyl oligopeptidase (POP) inhibitor isolated from Polyozellus multiplex, and its structure was assigned as 1 having a p-hydroquinone moiety by spectroscopic analyses and chemical means. This Letter describes the total syntheses of the proposed structure 1 for kynapcin-12 and 2',3'-diacetoxy-1,5',6',4″-tetrahydroxy-p-terphenyl 2 isolated from Boletopsis grisea, revising the structure of kynapcin-12 to the latter. These syntheses involved double Suzuki-Miyaura coupling, CAN oxidation, and LTA oxidation as key steps. The inhibitory activities of synthetic compounds against POP and cancer cells were also evaluated.

Detection of oxygen addition peaks for terpendole E and related indole-diterpene alkaloids in a positive-mode ESI-MS.

This report describes that a regular positive electrospray ionization mass spectrometry (MS) analysis of terpendoles often causes unexpected oxygen additions to form [M + H + O](+) and [M + H + 2O](+), which might be a troublesome in the characterization of new natural analogues. The intensities of [M + H + O](+) and [M + H + 2O](+) among terpendoles were unpredictable and fluctuated largely. Simple electrochemical oxidation in electrospray ionization was insufficient to explain the phenomenon. So we studied factors to form [M + H + O](+) and [M + H + 2O](+) using terpendole E and natural terpendoles together with some model indole alkaloids. Similar oxygen addition was observed for 1,2,3,4-tetrahydrocyclopent[b]indole, which is corresponding to the substructure of terpendole E. In tandem MS experiments, a major fragment ion at m/z 130 from protonated terpendole E was assigned to the substructure containing indole. When the [M + H + O](+) was selected as a precursor ion, the ion shifted to m/z 146. The same 16 Da shift of fragments was also observed for 1,2,3,4-tetrahydrocyclopent[b]indole, indicating that the oxygen addition of terpendole E took place at the indole portion. However, the oxygen addition was absent for some terpendoles, even whose structure resembles terpendole E. The breakdown curves characterized the tandem MS features of terpendoles. Preferential dissociation into m/z 130 suggested the protonation tendency at the indole site. Terpendoles that are preferentially protonated at indole tend to form oxygen addition peaks, suggesting that the protonation feature contributes to the oxygen additions in some degrees.

Structural elucidation and synthesis of vialinin C, a new inhibitor of TNF-α production.

A new inhibitor of TNF-α production (IC50=0.89 µM) named vialinin C (1) was isolated from dry fruiting bodies of an edible Chinese mushroom, Thelephora vialis. The structure of 1 was determined by high-resolution MS, NMR spectroscopic analysis, and confirmed by synthesis. Synthesis of ganbajunin B (5) obtained from the same origin was also described.

Ubiquitin-specific peptidase 5, a target molecule of vialinin A, is a key molecule of TNF-α production in RBL-2H3 cells.

Tumor necrosis factor alpha (TNF-α), a central mediator of the inflammatory response, is released from basophilic cells and other cells in response to a variety of proinflammatory stimuli. Vialinin A is a potent inhibitor of TNF-α production and is released from RBL-2H3 cells. Ubiquitin-specific peptidase 5 (USP5), a deubiquitinating enzyme, was identified as a target molecule of vialinin A and its enzymatic activity was inhibited by vialinin A. Here we report production of TNF-α is decreased in USP5 siRNA-knockdown RBL-2H3 cells, compared with control cells. The finding of the present study strongly suggests that USP5 is one of the essential molecules for the production of TNF-α in RBL-2H3.

Vialinin A is a ubiquitin-specific peptidase inhibitor.

Vialinin A, a small compound isolated from the Chinese mushroom Thelephora vialis, exhibits more effective anti-inflammatory activity than the widely used immunosuppressive drug tacrolimus (FK506). Here, we show that ubiquitin-specific peptidase 5/isopeptidase T (USP5/IsoT) is a target molecule of vialinin A, identified by using a beads-probe method. Vialinin A inhibited the peptidase activity of USP5/IsoT and also inhibited the enzymatic activities of USP4 among deubiquitinating enzymes tested. Although USPs are a member of thiol protease family, vialinin A exhibited no inhibitions for other thiol proteases, such as calpain and cathepsin.

Inhibitory effects of vialinin A and its analog on tumor necrosis factor-α release and production from RBL-2H3 cells.

Vialinin A is an extremely potent inhibitor of tumor necrosis factor (TNF)-α release from RBL-2H3 cells. The present study investigated in detail the inhibitory effects of vialinin A and its analog, 5',6'-dimethyl-1,1':4',1″-terphenyl-2',3',4,4″-tetraol (DMT), on TNF-α. Vialinin A and DMT inhibited the release of TNF-α from RBL-2H3 cells in a dose-dependent manner, but had no effect on ß-hexosaminidase activity. Also, vialinins had little effect on TNF-α mRNA levels. Intriguingly, vialinins inhibited TNF-α production at low concentrations, but not shown a dose-dependency. The potent inhibitory activities of vialinins against TNF-α production and release suggest promising new candidate pathways for anti-inflammatory agents.

Synthesis and biological activity of both enantiomers of kujigamberol isolated from 85-million-years-old Kuji amber.

The full-structure of a norlabdane terpenoid, kujigamberol (1) was determined by total synthesis. Key features of the total synthesis are (1) installation of isopentyl group through an o-lithiation of benzamide, (2) construction of tetralone by the RCM reaction, and (3) optical resolution of (±)-1 using chromatographical separation of the corresponding camphanates. X-ray crystallographical analysis of p-bromobenzoate obtained from the more polar camphanate that was identical with a natural derivative, revealed natural kujigamberol to have an S-configuration. Both the natural enantiomer and its (R)-antipode showed the same inhibitory activity toward the mutant yeast and HL-60 cells, while simple analogs without alkyl groups at the C-8 and 9 positions of (±)-1 had no such activity.

Kujigamberol, a new dinorlabdane diterpenoid isolated from 85million years old Kuji amber using a biotechnological assay.

A new compound, 15,20-dinor-5,7,9-labdatriene-18-ol (1), named kujigamberol, was isolated from amber, fossilized tree resin from the Kuji area in Japan, has been dated as being 85 million years old (late Cretaceous). Kujigamberol was identified using the hypersensitive mutant yeast (zds1∆ erg3∆ pdr1∆ pdr3∆) with respect to Ca(2+)-signal transduction. The structure was elucidated on the basis of spectroscopic analysis including 1D NMR, 2D NMR and HR-EI-MS. It was different from known diterpenoids with a similar activity isolated from Baltic amber (agathic acid 15-monomethyl ester (2), dehydroabietic acid (3) and pimaric acid (4)). Kujigamberol showed glycogen synthase kinase-3ß (GSK-3ß) inhibition activity involving the growth restored activity against the mutant yeast and was cytotoxic to HL60 cells (IC(50)=19.6 µM).