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The tetraene 7,7‐dimethoxy‐2,3,5,6‐tetramethylenebicyclo[2.2.1]heptane is a key compound for the preparation of a large variety of acenes protected by a carbonyl bridge. We report herein a medium scale preparation in seven steps of this valuable starting material. Diels–Alder addition between 6,6‐dimethtyl fulvene and maleic anhydride, followed by carboxylation, ozonolysis of the double bond, reduction of the four ester groups, then chlorination of the alcohol groups and dehydrochlorination give the target compound in 17 % overall yield. [ABSTRACT FROM AUTHOR]

Selective reduction of 1,5-diazacyclooctatetraenes with potassium or a Co(i) complex was achieved to provide the first structurally well-defined aromatic 1,5-diazacyclooctatetraenyl dianion or a novel dinuclear Co(ii) complex bridged by a bipyrrolinyl dianion, respectively. [ABSTRACT FROM AUTHOR]

Abstract Twenty-four diterpenoids of abietane family, including thirteen undescribed compounds and eleven known ones, were isolated from the leaves of Leucosceptrum canum. Their structures were elucidated by comprehensive spectroscopic analyses (including 1D and 2D-NMR and HRMS), and in the case of 15-hydroxy-abieta-8,11,13-trien-3-one by single-crystal X-ray diffraction. Their frameworks are highly diversified, involving normal abietane, 9,10-epoxy-9,10- seco -abietane, 18(4 → 3)- abeo -abietane, 3,4- seco -18(4 → 3)- abeo -abietane, and 16- nor -abietane. Selected compounds were evaluated for their cytotoxic activity against three human tumor cell lines, NCI-H1975, HepG2 and MCF-7. Among them, 3β-hydroxy-abieta-8,13-diene, 3β-hydroxy-abieta-8,11,13,15-tetraene, and 3β-hydroxy-9,10-epoxy-9,10- seco -abieta-8,11,13-triene exhibited moderate cytotoxicity against all three cell lines with IC 50 values ranging from 8.11 to 50.73 μM, while 3α-hydroxy-abieta-8,11,13,15-tetraene, 3β-hydroxy-abieta-8,11,13,15-tetraen-7-one, and 15-hydroxy-18(4 → 3)- abeo -abieta-3,8,11,13-tetraene were selectively active with IC 50 values ranging from 28.80 to 71.29 μM. Graphical abstract Thirteen undescribed abietane family diterpenoids along with eleven known ones were isolated from the aerial parts of Leucosceptrum canum. Six of them showed moderate cytotoxic activity. Image 1 Highlights • Twenty-four including 13 undescribed abietanoids were isolated from Leucosceptrum canum. • Their skeletons included normal, seco- , abeo -, seco - abeo- and nor -abietanes. • Six abietanoids showed moderate cytotoxicity against three tumor cell lines. • This is the first report of abietane family diterpenoids from Leucosceptrum canum. [ABSTRACT FROM AUTHOR]

A synthetic method to prepare bicyclo[6.3.0]undeca‐2,4,9,trienyl esters efficiently from gold(I)‐catalyzed Rautenstrauch rearrangement/1,5‐hydride shift/8‐endo‐dig cyclization of 1‐ene‐4,10‐diynyl esters is described. The suggested double cycloisomerization mechanism delineates the first example of an unactivated all‐carbon tethered 1,7‐enyne, either preformed or formed in situ, which undergoes an 8‐endo‐dig cyclization pathway to give a cyclooctane motif. It also offers an extremely rare synthetic method in organic chemistry that can sequentially assemble both ring components of the bicyclic motif from an acyclic precursor in one step. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First total synthesis of keto-tetraene 15-oxo-Lipoxin A4 has been achieved. • Synthetic approach: iterative palladium-catalyzed coupling using a MIDA boronate. • Dess-Martin oxidation of 15-position hydroxyl to electrophilic keto. • Key steps: Sonogashira, Suzuki couplings; Zinc(Copper/Silver) reduction of trien-yne. Abstract 15-oxo-Lipoxin A 4 (15-oxo-LXA 4) has been identified as a natural metabolite of the fatty acid signaling mediator Lipoxin A 4. Herein, we report a total synthesis of the methyl ester of 15-oxo-LXA 4 to be used in investigations of potential electrophilic bioactivity of this metabolite. The methyl ester of 15-oxo-LXA 4 was synthesized in a convergent 15 step (9 steps longest linear) sequence starting from 1-octyn-3-ol and 2-deoxy- d -ribose with Sonogashira and Suzuki cross-couplings of a MIDA boronate as key steps. [ABSTRACT FROM AUTHOR]

Bicyclo[4.3.1]deca-2,4,8-triene-7,10-diols were synthesized in 76–85% yields by oxidative skeletal isomerization of the substituted bicyclo[4.2.2]deca-2,4,7,9-tetraenes of various structures on treatment with m -chloroperbenzoic acid. The structures of the obtained bicyclic unsaturated diols were reliably proven by modern spectral methods and X-ray diffraction. A high antitumor activity in vitro was found for bicyclo[4.3.1]deca-2,4,8-triene-7,10-diols against the Jurkat, K562, U937 and HL-60 tumor cell lines. [ABSTRACT FROM AUTHOR]

Fusarithioamide B ( 6 ), a new aminobenzamide derivative with unprecedented carbon skeleton and five known metabolites: stigmast-4-ene-3-one ( 1 ), stigmasta-4,6,8(14),22-tetraen-3-one ( 2 ), p -hydroxyacetophenone ( 3 ), tyrosol ( 4 ), and fusarithioamide A ( 5 ) were separated from Fusarium chlamydosporium EtOAc extract isolated from Anvillea garcinii (Burm.f.) DC. leaves (Asteraceae). The structure elucidation and complete assignment of the isolated metabolites were performed mainly by the aid of various NMR and MS data. Fusarithioamide B ( 6 ) has been assessed for antibacterial and antifungal activities towards various microbial strains by disc diffusion assay. It exhibited selective antifungal activity towards C. albicans (MIC 1.9 µg/ml and IZD 14.5 mm), comparing to clotrimazole (MIC 2.8 µg/ml and IZD 17.9 mm). Also, it possessed high antibacterial potential towards E . coli , B. cereus , and S . aureus compared to ciprofloxacin. Furthermore, 6 was tested for the in vitro cytotoxic effect against KB, HCT-116, BT-549, MCF-7, SKOV-3, and SK-MEL cell lines. It had selective and potent effect towards BT-549, MCF-7, SKOV-3, and HCT-116 cell lines with IC 50 s 0.09, 0.21, 1.23, and 0.59 μM, respectively compared to doxorubicin (IC 50 s 0.046, 0.05, 0.321, and 0.24 μM, respectively). Fusarithioamide B may provide a lead molecule for future developing of antitumor and antimicrobial agents. [ABSTRACT FROM AUTHOR]

The Ru(0)-catalyzed straightforward synthesis of conjugated tetraenes has been achieved in up to 85% yield by coupling of 2 equiv of internal alkynes with 1,3-butadiene at room temperature. The stoichiometric reaction of [Ru(η4-cisoid-1,3-butadiene)(η4-1,5-COD)(NCMe)] with 2 equiv of 3-hexyne produces a tetraene complex of Ru(0), [Ru{3-6-η4-(3E,5E,7E,9E)-4,9-diethyldodeca-3,5,7,9-tetraene}(η4-1,5-COD)(NCMe)], in 98% yield, which releases the conjugated tetraene ligand in 92% yield by exposure to 1,3-butadiene. [ABSTRACT FROM AUTHOR]

Without employing high dilution conditions, the fourfold 2+2 Perkin reaction of 1,6-pyrenylene-diglyoxylic acid with its reduction product 1,6-pyrenylene-diacetic acid yields the corresponding tetrameric conjugated macrocycle in 25% overall yield after in-situ esterification. The macrocycle adopts a square fourfold symmetry in the crystal, with near-vertical pyrene walls that alternatingly tilt upwards and downwards. [ABSTRACT FROM AUTHOR]

In search of more effective chemotherapeutics for the treatment of castration-resistant prostate cancer and inspired by curcumin analogues, twenty five (1 E ,3 E ,6 E ,8 E )-1,9-diarylnona-1,3,6,8-tetraen-5-ones bearing two identical terminal heteroaromatic rings have been successfully synthesized through Wittig reaction followed by Horner–Wadsworth–Emmons reaction. Twenty-three of them are new compounds. The WST-1 cell proliferation assay was employed to assess their anti-proliferative effects toward both androgen-sensitive and androgen-insensitive human prostate cancer cell lines. Eighteen out of twenty-five synthesized compounds possess significantly improved potency as compared with curcumin. The optimal compound, 78 , is 14- to 23-fold more potent than curcumin in inhibiting prostate cancer cell proliferation. It can be concluded from our data that 1,9-diarylnona-1,3,6,8-tetraen-5-one can serve as a new potential scaffold for the development of anti-prostate cancer agents and that pyridine-4-yls and quinolin-4-yl act as optimal heteroaromatic rings for the enhanced potency of this scaffold. Two of the most potent compounds, 68 and 75 , effectively suppress PC-3 cell proliferation by activating cell apoptosis and by arresting cell cycle in the G 0 /G 1 phase. [ABSTRACT FROM AUTHOR]

The recent vibrational analysis of the experimental IR spectra of the non-planar gauche,Trans,trans,Trans,gauche possible rotational isomers of octa-1,3,5,7-tetraene (C i and C 2 ) is reconsidered. Calculations of the vibrational frequencies of the non-planar C i and C 2 conformers of C 8 H 10 and C 8 D 10 are performed. Some of the calculated vibrational frequencies of the non-planar C i conformer are reassigned. Comparison of the IR experimental frequencies with the calculated frequencies for the two non-planar conformers suggests that all experimental bands belong to the non-planar C 2 conformer. [ABSTRACT FROM AUTHOR]

Lucensomycin, tetraene macrolide antibiotic, has been chemically modified with dialkyl(diaryl) phosphites under conditions of the Todd-Atherton reaction. The reaction has yielded the corresponding dialkyl-(diaryl) amidophosphate derivatives of the antibiotic. Physico-chemical properties of the prepared derivatives as well as their toxicity and antifungal activity towards a series of pathogenic Candida yeast-like fungi have been studied. The automated decision-making information system for selection of highly efficient antibiotics has been described. [ABSTRACT FROM AUTHOR]

The equilibrium geometries of heptatriynylidene ( 1 ), cyclohepta-1,2,3,4-tetraen-6-yne ( 2 ), and heptahexaenylidene ( 3 ) have been theoretically investigated at various level of theories. The methods employed are Møller–Plesset perturbation level of theory until second-order, coupled-cluster singles and doubles (CCSD), and CCSD with perturbative triple excitations [CCSD(T)]. Correlation consistent polarized valence double and triple zeta (cc-pVXZ; X = D and T) basis sets are used in all calculations, which are compatible with the frozen-core approximation entreated in this study. The relative energies of the ground triplet electronic state ( X ∼ 3 Σ g - ) of 1 – the most stable isomer of C 7 H 2 – to the ground singlet electronic states of 2 ( X ∼ 1 A 1 ) and 3 ( X ∼ 1 A 1 ) have also been estimated at different levels. With zero-point vibrational energy corrections, 2 and 3 are found to lie ∼12.27 and ∼20.62 kcal mol −1 , respectively, above 1 at the highest level of theory (CCSD(T)/cc-pVTZ). While 1 and 3 are observed in the laboratory, 2 is a hypothetical molecule hitherto. Since the optimal geometry of 2 suggests the presence of biradical character, the singlet–triplet ( X ∼ 1 A 1 – 3 B 1 ) energy gap for isomer 2 was also calculated at various levels. The ab initio data presented here may be useful for the laboratory detection of 2 and astronomical detection of 2 and 3 . [ABSTRACT FROM AUTHOR]

A sequence of two Diels-Alder reactions is observed for the reaction of bis-diene (E)-3-[2-(furan-2-yl)vinyl]-5,5-dimethylcyclohex-2-en-1-one with two equivalents of N-phenylmaleimide. This study shows that the electron-deficient furanyl site, which is primarily 'inactive' towards a [4 + 2] reaction, easily undergoes cycloaddition with the second equivalent of N-phenylmaleimide to produce the final bisadduct. This is because the first Diels-Alder reaction between N-phenylmaleimide and the more reactive cyclohex-2-en-1-one site of the diene converts the 2-furanyl ring to a more electron-rich component, since the electron-withdrawing double bond attached to the furan ring changes to an electron-releasing alkyl group after the first cycloaddition. Consequently, the resulting furanyl diene is then able to undergo the second cycloaddition. [ABSTRACT FROM AUTHOR]

Preparations of Echinacea purpurea ( E. purpurea ) are widely used for the management of upper respiratory infections, influenza, and common cold, often in combination with other conventional drugs. However, the potential of phytochemical constituents of E. purpurea to cause herb-drug interactions via ABCB1 and ABCG2 efflux transporters remains elusive. The purpose of this study was to investigate the impact of E. purpurea -derived caffeic acid derivatives (cichoric acid and echinacoside) and tetraenes on the mRNA and protein expression levels as well as on transport activity of ABCB1 and ABCG2 in intestinal (Caco-2) and liver (HepG2) cell line models. The safety of these compounds was investigated by estimating EC 20 values of cell viability assays in both cell lines. Regulation of ABCB1 and ABCG2 protein in these cell lines were analyzed after 24 h exposure to the compounds at 1, 10, and 50 μg/mL. Bidirectional transport of 0.5 μg/mL Hoechst 33342 and 5 μM rhodamine across Caco-2 monolayer and profiling for intracellular concentrations of the fluorophores in both cell lines were conducted to ascertain inhibition effects of the compounds. Cichoric acid showed no cytotoxic effect, while the EC 20 values of tetraenes and echinacoside were 45.0 ± 3.0 and 52.0 ± 4.0 μg/mL in Caco-2 cells and 28.0 ± 4.3 and 62.0 ± 9.9 μg/mL in HepG2 cells, respectively. In general, the compounds showed heterogeneous induction of ABCB1 with the strongest 3.6 ± 1.2-fold increase observed for 10 μg/mL tetraenes in Caco-2 cells ( p < 0.001). However, the compounds did not induce ABCG2. None of the phytocompounds inhibited significantly net flux of the fluorophores across Caco-2 monolayers. Overall, tetraenes moderately induced ABCB1 but not ABCG2 in Caco-2 and HepG2 cells while no compound significantly inhibited activity of these transporters at clinically relevant concentration to cause herb-drug interactions.

Reaction of dienone (I) with two equivalents of N-phenylmaleimide proceeds as a sequence of two sequential Diels-Alder reactions furnishing the bis-adduct (III) in excellent yield. [ABSTRACT FROM AUTHOR]

Symmetrical spiro-1,3-bisketone (IV) is synthesized by ring-closure metathesis reaction of tetraene (I) obtained by Grignard reaction of a dialkenyl compound and allylmagnesium bromide. [ABSTRACT FROM AUTHOR]

A wide variety of primary and secondary amines are suitable nucleophiles for the title reaction to form ring opening products with good levels of enantioselectivity. [ABSTRACT FROM AUTHOR]