Amphirionin-5, a novel linear polyketide from a cultured marine dinoflagellate Amphidinium species with a potent cell proliferation-promoting activity

A novel linear polyketide, amphirionin-5 (1), has been isolated from the cultivated algal cells of the benthic dinoflagellate Amphidinium sp. (strain KCA09053), and the structure was elucidated on the basis of detailed analyses of 1D and 2D NMR data. Amphirionin-5 (1) resulted in a 282% increase in the proliferation of murine bone-marrow derived stromal ST-2 cells and 320% increase in the proliferation of murine osteoblastic MC3T3-E1 cells.     

Amphezonol A, a novel polyhydroxyl metabolite from marine dinoflagellate Amphidinium sp.

Amphezonol A (1), a novel polyhydroxyl linear carbon-chain metabolite, has been isolated from the cultured marine dinoflagellate Amphidinium sp., which was isolated from an Okinawan marine acoel flatworm Amphiscolops sp. The structure of 1 was elucidated by detailed analyses of 2D NMR spectra. Amphezonol A (1) possesses one tetrahydrofuran ring, two tetrahydropyran rings, and twenty-one hydroxyl groups on C₆₀-linear aliphatic chain with one exo-methylene and one methyl branch. Amphezonol A (1) exhibited a modest inhibitory activity against DNA polymerase α.     

Iriomoteolide-3a, a cytotoxic 15-membered macrolide from a marine dinoflagellate amphidinium species

A 15-membered macrolide, iriomoteolide-3a (1), with an allyl epoxide has been isolated from a marine benthic dinoflagellate Amphidinium sp. (strain HYA024), and the structure was assigned by detailed analyses of 2D NMR data. Relative and absolute configurations were elucidated on the basis of conformational studies of 1 and its acetonide (2) and modified Mosher's method of 1, respectively. Iriomoteolide-3a (1) and the acetonide (2) exhibited potently cytotoxic activity against antitumor cells.     

Karatungiols A and B, two novel antimicrobial polyol compounds, from the symbiotic marine dinoflagellate Amphidinium sp.

Karatungiols A (1) and B (2), two novel antimicrobial polyol compounds, were isolated from the cultivated symbiotic marine dinoflagellate Amphidinium sp. Their structures were elucidated based on spectroscopic analysis and degradation reactions. Karatungiols A (1) and B (2) consisted of a C69-linear chain with a ketone moiety, 24 or 25 hydroxyl groups, and two tetrahydropyran rings. Karatungiol A (1) exhibited antifungal activity against Aspergillus niger at 12 μg/disc and antiprotozoan activity against Trichomonas foetus at 1 μg/ml.     

Iriomoteolide-1a, a potent cytotoxic 20-membered macrolide from a benthic dinoflagellate amphidinium species

A potent cytotoxic 20-membered macrolide, iriomoteolide-1a (1), has been isolated from a benthic dinoflagellate Amphidinium sp. (strain HYA024), and the structure was elucidated on the basis of detailed analyses of 2-D NMR data. The relative and absolute stereochemistries were assigned by the combination of conformational analyses using NMR data and modified Mosher's method of 1.     

Symbiodinolactone A,a new 12-membered macrolide from symbiotic marine dinoflagellate Symbiodinium sp.

A new 12-membered macrolide, symbiodinolactone A, was isolated from the culture broth of symbiotic marine dinoflagellate Symbiodinium sp. The gross structure of symbiodinolactone A was elucidated by spectroscopic analyses, and the relative configuration was elucidated by the J-based configuration analysis and density-functional theory calculations. Symbiodinolactone A is the new 12-membered macrolide possessing an E double bond between C-4 and C-5, a branched methyl group at C-7, and a 1,2,3-trihydroxybutyl group at C-11. Symbiodinolactone A is the first usual size macrolide and the first non-nitrogen-containing macrolide from dinoflagellate Symbiodinium sp. Symbiodinolactone A might be generated by the unexplained dinoflagellate polyketide biosynthetic machinery.     

Sanctolide A, a 14-membered PK-NRP hybrid macrolide from the cultured cyanobacterium Oscillatoria sancta (SAG 74.79)

Sanctolide A (1), a 14-membered polyketide-nonribosomal peptide (PK-NRP) hybrid macrolide, was isolated from the cultured cyanobacterium Oscillatoria sancta (SAG 74.79). The planar structure was determined using various spectroscopic techniques including HRESIMS, and 1D and 2D NMR analyses. The relative configuration was assigned by J-based configurational analysis in combination with NOE correlations. The absolute configuration was determined by Mosher ester and enantioselective HPLC analyses. The structure of sanctolide A (1) features a rare N-methyl enamide and a 2-hydroxyisovaleric acid, which are incorporated to form a 14-membered macrolide ring structure, comprising a new type of cyanobacterial macrolides derived from a PKS-NRPS hybrid biosynthetic pathway.     

2-Benzyliden-2H-thieto[3,2-b]quinoline: a new heterocycle and its rearrangement to 2-phenylthieno[3,2-b]quinoline

Synthesis of the strained 2H-thieto[3,2-b]quinoline ring system is reported for the first time. Treatment of (Z)-2-benzyliden-2H-thieto[3,2-b]quinoline derivatives of this heterocycle with base, at reflux in ethanol, causes a novel rearrangement to 2-phenylthieno[3,2-b]quinolines. Indeed, the one-pot reaction of 2-aminobenzaldehydes and (Z)-2-benzylidenethietan-3-one in refluxing basic ethanol leads directly to 2-phenylthieno[3,2-b]quinolines in good yields.     

Polyhydroxylated macrolide isolated from the endophytic fungus Pestalotiopsis mangiferae

A new polyhydroxylated macrolide, named mangiferaelactone (1) was isolated from a solid culture of the endophytic fungus Pestalotiopsis manguiferae, together with ten known compounds [(6S,1′S)-LL-P880α; (6S,1′S,2′R)-LL-P880β; (1′S,2′R)-LL-880γ; (1′R)-dehydropestalotin; (−)-5-carboxylmellein; (−)-5-methylmellein; (−)-5-hydroxylmethylmellein; arabenoic acid; 5,6-dihydro-4-methoxy-2H-pyran-2-one; and the (−)-2-hexylidene-3-methylsuccinic acid]. P. manguiferae was isolated from Hyptis dilatata, a small shrub common in the central region of Panama. The structure of compound 1 was elucidated by a combination of spectroscopic methods (IR, MS, optical rotation, 1D and 2D NMR spectroscopy). The absolute configuration of 1 was established as 4R,7R,8R,9S by application of vibrational circular dichroism (VCD). Compound 1 showed a minimum inhibitory concentration (MIC) of 1.6863 mg/mL against Listeria monocytogenes, and 0.5529 mg/mL against Bacillus cereus. No activity was observed for compound 1 against Plasmodium falciparum or Trypanosoma cruzi; likewise, no cytotoxic activity was observed against A2058 and H522-T1 cells.     

Unexpected nitrilimine cycloaddition of thiazolo[3,2-a]pyrimidine derivatives

1,3-Dipolar cycloaddition of 2-arylidene-6,7-dihydro-5H-thiazolo[3,2-a]pyrimidine-3(5H)-ones to diphenylnitrilimine (generated in situ by triethylamine dehydrohalogenation of the N′-phenylbenzohydrazonoyl chloride) proceeded regio- and site-selectively affording a mixture of two unexpected isomer products at reflux temperature. The cycloaddition/ring-opening/rearrangement/substitution, mechanism of the reaction was also discussed.     

New cytotoxic sesquiterpenes from the red algae Laurencia obtusa and Laurencia microcladia

Three new sesquiterpenes (1-3), along with five known (5-9), were isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Serifos in the Aegean Sea. A new dimeric sesquiterpene of the cyclolaurane-type (4) along with four previously reported (7, 10-12) metabolites, were isolated from the extract of Laurencia microcladia, collected at Chios island in the North Aegean Sea. The structures and the relative stereochemistry of the compounds are proposed on the basis of their spectral data. The cytotoxicity of the isolated metabolites was evaluated against several cell lines including human tumor cell lines.     

Furo[3,2-h]isochroman, furo[3,2-h]isoquinoline, isochroman, phenol, pyranone, and pyrone derivatives from the sea fan-derived fungus Penicillium sp. PSU-F40

Nine new fungal metabolites, penicisochromans A-E, penicipyrone, penicipyranone, peniciphenol, and penicisoquinoline, were isolated from the sea fan-derived fungus Penicillium sp. PSU-F40 together with five known compounds. Their structures were determined by spectroscopic analysis. Their antibacterial activity against the standard Staphylococcus aureus ATCC 25923 and methicillin-resistant S. aureus was evaluated.     

Zyzzyanone A, a novel pyrrolo[3,2-f]indole alkaloid from the Australian marine sponge Zyzzya fuliginosa

A new dipyrroloquinone, zyzzyanone A 1, having a pyrrolo[3,2-f]indole-4,8(1H,7H)-dione skeleton, was isolated from the Australian marine sponge Zyzzya fuliginosa, along with the known pyrroloquinoline alkaloids, makaluvamines C, E, G, H, and L, and damirones A and B. The structure of 1 was determined by spectroscopic data. Zyzzyanone A 1 shows moderate cytotoxic activity against mouse Ehrlich carcinoma cells (IC₅₀ 25 μg/mL), inhibits the cell division of fertilized sea urchin eggs at a concentration of 25 μg/mL, and exhibits UV-A and UV-B absorbing activity.     

Synthesis and some transformations of new 9-furylnaphtho[2,3-b]furan derivatives

The synthesis of a number of naphtho[2,3-b]furan derivatives, containing a furyl substituent in position 9 by intramolecular cyclization of 2-carboxy and 2-formylbis(5-alkylfur-2-yl)methanes is described. The reactivity of the title compounds in formylation, acetylation, nitration, and oxidation reactions has been investigated. It was shown that nitration of 2-methyl-9-(5-methyl-2-furyl)naphtho[2,3-b]furan-4-yl acetate leads to oxidative furan ring opening rather than to electrophilic substitution.     

Novel cytotoxic kaurane-type diterpenoids from the New Zealand Liverwort Jungermannia species

Novel cytotoxic rearranged kaurene- and ent-kaurene-type diterpenoids against HL-60 cells have been isolated from the unidentified New Zealand liverwort Jungermannia species together with previously known ent-kaurane-type diterpenoids. Their structures were determined by extensive NMR techniques, chemical degradation and X-ray crystallographic analysis.     

Exiguolide, a new macrolide from the marine sponge Geodia exigua

A new 20-membered macrolide designated exiguolide has been isolated from the marine sponge Geodia exigua, and its structure determined by interpretation of spectroscopic data. Exiguolide specifically inhibited fertilization of sea urchin (Hemicentrotus pulcherrimus) gametes but not embryogenesis of the fertilized egg.     

One pot synthesis of imidazo[2,1-b]thiazoles and benzo[d]thiazolo[3,2-a]imidazoles

A series of imidazo[2,1-b]thiazole and benzo[d]thiazolo[3,2-a]imidazole analogues were synthesized by stirring an equimolar mixture of dibenzoylacetylene with imidazole/thiazole derivatives in toluene or acetonitrile at room temperature. The products were generated in good yields and characterized by standard analytical techniques such as IR, ¹H NMR, ¹³C NMR and mass spectrometry. The structure of products 19, 20, 22, 24 and 25 were also unambiguously confirmed by single crystal X-ray analysis.     

Intramolecular 4+2 cycloaddition of thieno[2,3-e][1,2,4]triazines: routes towards condensed thieno[2,3-b]pyridines

Synthetic approaches towards new condensed thienopyridine ring systems including furo[2,3-b]thieno[3,2-e]pyridines, bisthieno[2,3-b:3′,2′-e]pyridines, 5H-chromeno[2,3-b]thieno[3,2-e]pyridines, 5H-benzo(f)chromeno[2,3-b]thieno[3,2-e]pyridines have been achieved by application of intramolecular 4+2 cycloaddition reactions of suitably designed thieno[2,3-e][1,2,4]triazines tethered with alkene or alkyne terminals.     

Novel cytotoxic icetexane diterpenes from Premna latifolia Roxb

Chromatographic fractionation of a hexane extract from stem-bark of Premna latifolia yielded three new icetexane diterpenes (1-3). Their structures were elucidated on the basis of spectroscopic data, mainly NMR and MS, data. Compounds 1-3 were also evaluated for the cytotoxicity against the cancer cell lines (HT-29, A-431, MCF-7, Hep-G2, PC-3, A-549, B-16 F10 and ACHN). Compounds 1 and 2 displayed potent cytotoxic activity against HT-29 and Hep-G2 cell lines with IC₅₀ values of 0.04 and 0.18 μg/mL, respectively.     

Antimalarial 20-membered macrolides from Streptomyces sp. BCC33756

Two new natural products, samroiyotmycins A (1) and B (2), along with two naturally new novclobiocin 101 (3) and 4-hydroxy-3-(3-methylbut-2-enyl)benzamide (5), and five known substances including neoantimycin, clorobiocin (4), 29-O-methylabierixin, daidzein, and 1-(3-indolyl)-2,3-dihydroxypropan-1-one have been isolated from Streptomyces sp. BCC33756. Their chemical structures were determined based on NMR spectral information and the relative stereochemistry of compound 1 was determined by X-ray crystallographic data. Both samroiyotmycins A and B exhibited antimalarial activity against Plasmodium falciparum K1—multi-drug resistant strain, with IC₅₀ values of 3.65 and 3.16 μg/mL, respectively. Compound 1 was inactive against both cancerous (MCF-7, KB) and non-cancerous (Vero) cells, while compound 2 displayed cytotoxicity against Vero cell with IC₅₀ value of 29.57 μg/mL.