Hamigeromycins C-G, 14-membered macrolides from the fungus Hamigera avellanea BCC 17816

Five new 14-membered macrolides, hamigeromycins C-G, together with the previously described compounds, hamigeromycin A and 89-250904-F1 (radicicol analog A), were isolated from the fungus Hamigera avellanea BCC 17816. Hamigeromycins A, C, D, and E are stereoisomers differing from one another in the absolute configurations of the 4′,5′-diol moiety. Hamigeromycins F and G are unusual 5′-keto-analogs, and they are 6′-epimers to each other. The structures and the stereochemistry of the new compounds were deduced by analyses of the NMR spectroscopic and mass spectrometry data in combination with chemical means.     

Lanostane triterpenoids from cultivated fruiting bodies of the basidiomycete Ganoderma australe

A new lanostane triterpene (1), together with three known compounds (2–4), were isolated from cultivated fruiting bodies of the basidiomycete Ganoderma australe. The structure was elucidated on the basis of NMR spectroscopic and mass spectrometry data. The olefinic geometry of methyl australate (2) was revised from 20(22)Z to 20(22)E. These compounds (1–4) were different from the lanostanes isolated from mycelial cultures of the same strain source.     

Density functional study of the complete pathway for the Heck reaction with palladium diphosphines

The reaction mechanism for the complete catalytic cycle of the Heck reaction (between phenyl bromide, C₆H₅Br, and ethylene, C₂H₄, in the presence of the base, NEt₃ to form the product styrene, C₆H₅–C₂H₃), catalyzed by diphosphinopalladium complexes, Pd(PR₃)₂ {R = H, Me, Ph}, was investigated by using density functional theory (DFT). The relative free energies of the fully-optimized species in gas phase at 298.15 K and 1 atm were corrected for solvation in DMSO at 1 mol/L by using conductor-like polarizable continuum model (CPCM). The calculations indicate a four-step mechanism for the catalysis, including oxidative addition of C₆H₅Br, migratory insertion of C₆H₅ to C₂H₄, β-hydride transfer/olefin elimination of product, and catalyst regeneration by removal of HBr. Our calculations demonstrate that Pd π-complexes can be formed with phenyl bromide and ethylene before the oxidative addition occurs. Subsequently, various reaction paths were studied for the oxidative addition of phenyl bromide to palladium complexes, coordinated by phosphine(s) and/or ethylene. Interestingly, all pathways lead to palladium monophosphine as the active catalyst. Careful exploration was made on two possible pathways for the migratory insertion and β-hydride-transfer/olefin elimination: (1) the neutral path with bromide bound to Pd and (2) the cationic path with prior bromide ion dissociation. The neutral path is preferred to the cationic path, especially when the more bulky phosphines such as triphenylphosphine are involved.     

Salicylaldehyde and dihydroisobenzofuran derivatives from the marine fungus Zopfiella marina

Two salicylaldehyde derivatives (1 and 2), a hydroxymethylphenol (3), five dihydroisobenzofuran (4–8) derivatives, and a 5-chloro-3-deoxyisoochracinic acid (9), together with a known 3-deoxyisoochracinic acid (10) were isolated from the marine fungus Zopfiella marina BCC 18240 (or NBRC 30420). The structures of these compounds were elucidated by extensive spectroscopic analysis. Compound 1 showed weak antituberculous activity against Mycobacterium tuberculosis H37Ra, and antibacterial activity against Bacillus cereus with MIC values of 25 and 12.5 μg/mL, respectively.     

Influences of peripherally-cut twisted tape insert on heat transfer and thermal performance characteristics in laminar and turbulent tube flows

Effects of peripherally-cut twisted tape insert on heat transfer, friction loss and thermal performance factor characteristics in a round tube were investigated. Nine different peripherally-cut twisted tapes with constant twist ratio (y/W = 3.0) and different three tape depth ratios (DR = d/W = 0.11, 0.22 and 0.33), each with three different tape width ratios (WR = w/W = 0.11, 0.22 and 0.33) were tested. Besides, one typical twisted tape was also tested for comparison. The measurement of heat transfer rate was conducted under uniform heat flux condition while that of friction factor was performed under isothermal condition. Tests were performed with Reynolds number in a range from 1000 to 20,000, using water as a working fluid. The experimental results revealed that both heat transfer rate and friction factor in the tube equipped with the peripherally-cut twisted tapes were significantly higher than those in the tube fitted with the typical twisted tape and plain tube, especially in the laminar flow regime. The higher turbulence intensity of fluid in the vicinity of the tube wall generated by the peripherally-cut twisted tape compared to that induced by the typical twisted tape is referred as the main reason for achieved results. The obtained results also demonstrated that as the depth ratio increased and width ratio decreased, the heat transfer enhancement increased. Over the range investigated, the peripherally-cut twisted tape enhanced heat transfer rates in term of Nusselt numbers up to 2.6 times (turbulent regime) and 12.8 times (laminar regime) of that in the plain tube. These corresponded to the maximum performance factors of 1.29 (turbulent regime) and 4.88 (laminar regime).     

Utilization of Agricultural Residues of Pineapple Peels and Sugarcane Bagasse as Cost-Saving Raw Materials in Scenedesmus acutus for Lipid Accumulation and Biodiesel Production

The aim of this study is to optimize the lipid accumulation in microalgae by using two agricultural residues of pineapple peels and sugarcane bagasse as low-cost organic carbon sources. Green microalgae Scenedesmus acutus was isolated and selected for cultivation. Effects of three initial sugar concentrations and the stage for adding sugar during cultivation on biomass and lipid production were investigated. The results clearly showed that two-stage cultivation is more suitable than one-stage. The maximum biomass concentration and productivity were obtained at 3.85 g/L and 160.42 mg/L/day when sugarcane bagasse was used. The highest lipid content and lipid yield was reached at 28.05 % and 0.93 g/L when pineapple peels were used, while in the case of sugarcane bagasse, 40.89 % and 1.24 g/L lipid content and yield were obtained. Lipid content was found in normal condition (autotrophic) at 17.71 % which was approximately 2.13-fold lower than when sugarcane bagasse was used (40.89 %). Biodiesel production via in situ transesterification was also investigated; the main fatty acids of palmitic acid and oleic acid were found. This work indicates that using agricultural residues as organic carbon sources could be able to increase lipid content and reduce the cost of biofuel production.     

Novel cyclopropyl diketones and 14-membered macrolides from the soil fungus Hamigera avellanea BCC 17816

Two novel cyclopropyl diketones, hamavellone A (1) and B (2), and two new 14-membered nonaketide macrolactones, hamigeromycin A (3) and B (4), together with six known compounds, 89-250904-F1 (radicicol analogue A, 5), pseurotin A (6), emodin (7), ω-hydroxyemodin (8), and emodin bianthrones (9 and 10) were isolated from the soil fungus Hamigera avellanea BCC 17816. The structures of the new compounds were defined by analysis of NMR and MS data. The absolute stereochemistry of 3 was addressed by chemical correlation to 5. Hamavellone B (2) exhibited antimalarial activity with an IC₅₀ of 5.2 μg/mL, whereas it also showed comparable cytotoxicity.     

Lanostane triterpenoids from fruiting bodies of the bracket fungus Fomitopsis feei

Three 24-methyl-lanostane triterpenoids, fomitopsins D–F (1–3), were isolated together with four known compounds (4–7) from fruiting bodies of the basidiomycete Fomitopsis feei. The structures were elucidated by spectroscopic analysis and chemical correlations, including the conversion of 1 into a mixture of 2 and 3 under acidic conditions. Compound 1 was previously isolated after conversion to a methyl ester derivative, however, the side-chain stereochemistry was not determined. Fomitopsins E (2) and F (3) exhibited activity against Bacillus cereus with MIC values of 6.25 μg/mL. On the other hand, fomitopsin D (1) showed activity against herpes simplex virus type 1 (HSV-1) with an IC₅₀ value of 17 μg/mL.     

Synthesis,optical, and electrochemical properties,and theoretical calculations of BODIPY containing triphenylamine

The boron dipyrromethene (BODIPY) triads consisting of two triphenylamine units as electron donor (D) and BODIPY core as electron acceptor (A; B3 , and B4 ) have been synthesized using facile palladium cross‐coupling reactions to broaden the absorption of the BODIPY dyes. All dyes and intermediates were characterized by ¹H NMR, ¹¹B NMR, ¹³C NMR, and ¹⁹F NMR spectroscopies, UV–Vis spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and time‐dependent density functional theory calculations. It was found that an increase in conjugation to the BODIPY core systematically extended the absorption and emission wavelength maxima. As a consequence, B4 containing the D–π–A–π–D structure, exhibited the longest absorption and emission maxima at 597 and 700 nm, respectively, with 1.8 eV in optical bandgap. The 96 nm red‐shifted absorption of B4 as compared to the unsubstituted BODIPY ( B1 ) indicated the effective electronic communication between triphenylamine and BODIPY. This suggested that the proper alignment of triphenylamine and BODIPY triad could lead to broader absorption and suitable low energy bandgap. Furthermore, the molecular modeling has been employed to analyze the electronic and optical properties of the dyes. We found that the optical, electrochemical, and theoretical bandgaps of all dyes were in good agreement.