Synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate

The first total synthesis of methyl (5Z,8Z,10E,12E,14Z)-eicosapentaenoate has been achieved in seven steps and in 16% overall yield. The synthesis confirmed the assigned structure of this polyunsaturated natural product.     

A facile approach for the synthesis of 14-aryl- or alkyl-14H-dibenzo[a,j]xanthenes under solvent-free condition

A facile, efficient and environment-friendly protocol for the synthesis of 14-aryl- or alkyl-14H-dibenzo[a,j]xanthenes has been developed by one-pot condensation of 2-naphthol with aliphatic and aromatic aldehydes in the presence of P₂O₅ or InCl₃ as catalysts under solvent-free conditions. The present approach offers the advantages of clean reaction, simple methodology, short reaction time, high yield, easy purification, and economic availability of the catalyst.     

Chemoenzymatic synthesis and HPLC analysis of the stereoisomers of miyakosyne A [(4E,24E)-14-methyloctacosa-4,24-diene-1,27-diyne-3,26-diol], a cytotoxic metabolite of a marine sponge Petrosia sp., to determine the absolute configuration of its major component as 3R,14R,26R

Six samples [(3R,14R,26R)-, (3R,14S,26R)-, (3S,14R,26S)-, and (3S,14S,26S)-1, a mixture of (3R,14R,26S)- and (3S,14R,26R)-1, and a mixture of (3R,14S,26S)- and (3S,14S,26R)-1] of miyakosyne A [1, (4E,24E)-14-methyloctacosa-4,24-diene-1,27-diyne-3,26-diol] were synthesized starting from the enantiomers of citronellal (2), employing olefin cross metathesis and R-selective asymmetric acetylation of a stereoisomeric mixture of acetylenic alcohols with vinyl acetate and lipase PS as key reactions. Separation of the eight stereoisomer of 1 by reversed phase HPLC at −56 °C was achieved after their esterification with (1R,2R)-2-(anthracene-2,3-dicarboximido)cyclohexanecarboxylic acid (16), and the natural miyakosyne A was found to be a mixture of 95.7% of (3R,14R,26R)-1 and 4.3% of (3R,14S,26R)-1. This is different from the (3R,14S,26R)-configuration of 1 as tentatively assigned by X-ray analysis.     

Hydrogen cycling induced diffraction peak broadening in C14 and C15 Laves phases

The diffraction peak broadening induced by hydrogen absorption-desorption cycling has been analyzed in four different Laves phase compounds with the C14 and C15 structures. The broadening is due to strain most probably originating from dislocations generated at the interface between the α and β hydride phases in connection with the cell volume difference between the two phases. It has been shown that it is strongly compound dependent. In the case of the C14 structure, the broadening is large and isotropic, and the latter can be related to the isotropy of the elastic constants of the metallic phase. The broadening is less for the compounds with the C15 structure, which can be related to a possibly softer lattice. Better ageing properties after long-term cycling are predicted for this crystal structure.     

Photon-echo relaxation measurements with two dye-lasers application to pentacene-h14 and -d14 in p-terphenyl-h crystals at 1.5 K

Electronically controlled photon-echo relaxation measurements, using two nitrogen pumped dye-lasers, are reported for mixed crystals of pentacene-h₁₄ and -d₁₄ in p-terphenyl-h₁₄ at 1.5 K. In dilute mixed crystals (ca. 10^?8 M) the photon-echo lifetime is found to be exclusively determined by the fluorescence lifetime. Homogeneous linewidths of 7.1 and 5.9 MHz at 1.5 K are then calculated for the electronic origin of the ¹B_2u ← ¹A_1g transition of pentacene-h₁₄ and -d₁₄ respectively. The decrease in photon-echo lifetime at higher guest concentrations (ca. 10^?7 M) is ascribed to energy transfer between excited and neutral guest molecules.     

A stereoselective synthesis for the (5Z,9Z)-14-methyl-5,9-pentadecadienoic acid and its monounsaturated analog (Z)-14-methyl-9-pentadecenoic acid

A stereoselective synthesis for the (5Z,9Z)-14-methyl-5,9-pentadecadienoic acid and the monounsaturated analog (Z)-14-methyl-9-pentadecenoic acid was accomplished in six to seven steps where double alkyne coupling was the key step. This synthesis will facilitate the study of the topoisomerase I inhibitory profile of this important class of fatty acids.     

Enantioselective synthesis of (8S,13S,14R)-7-oxa-estra-4,9-diene-3,17-dione

The first enantioselective synthesis of (8S,13S,14R)-7-oxa-estra-4,9-diene-3,17-dione with the trans-C/D ring junction is described. Key features of the synthesis include Ag₂O-mediated C-O bond formation, thermodynamically controlled axial-equatorial inversion, one-pot of halogen exchange and Co/Cr-mediated C-C bond formation, and intramolecular aldol condensations.     

Synthesis of bridged nicotinates having [n](2,5)pyridinophane skeletons (n=8-14)

Synthesis of various bridged nicotinates 6 having [n](2,5)pyridinophane skeletons (n=8-14) was accomplished by the unique pyridine-formation reaction of methyl propiolate with a series of formyl-substituted (vinylimino)phosphoranes 5, which were prepared from the corresponding cycloalkanones 1 via Vilsmeier-Haack formylation giving chloro-substituted cycloalkenals 2, their thermal and photochemical transformation to formyl azirines 4, and the following ring-opening reactions with triphenylphosphine. The HPLC analysis of [11](2,5)pyridinophane derivatives, (S_p,S)-14 and (R_p,S)-14, showed that these diastereomers rapidly epimerize themselves at room temperature and that their planar-chirality was thermodynamically less stable as compared to the corresponding [11](2,5)cyclophane systems.     

Stereoselective synthesis of rac-(8R,13S,14S)-7-oxa-estra-4,9-diene-3,17-dione

The first synthesis of a novel oxa-steroid, rac-(8R,13S,14S)-7-oxa-estra-4,9-diene-3,17-dione has been achieved via stereoselective catalytic hydrogenation of the tetra-substituted indene intermediate, whose structure was confirmed by X-ray crystallography. In contrast to the previous reports of similar indene systems, it was found that catalytic hydrogenation of indenes with a large substituent at the C-2 position and a bulky β-oriented protective group at the C-6 position resulted in cis-indanes instead of trans-indanes.     

Lissoclibadins 8-14, polysulfur dopamine-derived alkaloids from the colonial ascidian Lissoclinum cf. badium

Seven new polysulfur alkaloids, lissoclibadins 8 (1)-14 (7), were isolated from an ascidian, Lissoclinum cf. badium, collected in Indonesia. The structures were assigned on the basis of their spectroscopic data and computational modeling study. Lissoclibadin 8 (1) had four identical dopamine-derived units, and this is the first instance of a tetramer. Lissoclibadin 9 (2) was the second example of trimers next to lissoclibadin 1 (8). Lissoclibadins 10 (3)-12 (5) were symmetric dimers, and 13 (6) had a dopamine and ethyl units connected by sulfide and disulfide bonds. Lissoclibadin 14 (7) was a varacin-type monomer. These compounds inhibited the colony formation of Chinese hamster V79 cells and cell proliferation of murine leukemia L1210 cells.     

A flexible route to immunosuppressive agent FR252921. Asymmetric total synthesis of its (13R,14R,19R)-isomer

A flexible route to the proposed structure of FR252921, a novel immunosuppressive agent, is developed. The key elements include the assembly of its two β-hydroxy acid residues via asymmetric aldol condensation of N-acylthiazolidinethinones with aldehydes, and its triene part via a CuI/N,N-dimethylglycine catalyzed Sonogashira coupling and subsequent isomerization. Using this strategy (13R,14R,19R)-FR252921 is elaborated.     

Blennolide derivatives from the soil-derived fungus Trichoderma asperellum PSU-PSF14

Three new blennolide derivatives, blennolides L-N (1–3), together with five known metabolites were isolated from the soil-derived fungus Trichoderma asperellum PSU-PSF14. Their structures were determined by analysis of spectroscopic data. Their relative configurations were determined by analysis of NOEDIFF data and confirmed by X-ray crystallography for compound 1 whereas the absolute configurations were established by means of experimental and calculated TDDFT ECD data. Compound 1 displayed antifungal activity against Cryptococcus neoformans ATCC90112 and ATCC90113 flucytosine-resistant with the MIC values of 128 and 64?μg/mL, respectively, and was inactive against noncancerous Vero cell lines.     

BF3·SiO2: an efficient alternative for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes

Silica-supported boron trifluoride (BF₃·SiO₂) is an efficient, readily available, and reusable catalyst for the synthesis of 14-aryl or alkyl-14H-dibenzo[a,j]xanthenes by condensation of 2-naphthol and aldehydes. This reaction under heating or sonication conditions is very simple, affording good to excellent yields of products.     

A class of 18(13→14)-abeo-schiartane skeleton nortriterpenoids from Schisandra propinqua var. propinqua

A class of C₂₉ triterpene dilactones (1-6) featuring 18(13→14)-abeo-schiartane skeleton have been isolated from the stems of Schisandra propinqua var. propinqua. The structures of new compounds, propindilactones K-O (1-5), were determined on the basis of comprehensive spectroscopic means. Biogenetic pathway of 1-6 was proposed and then chemically mimicked. The absolute stereochemistries of new compounds were established on biosynthetic consideration coupled with CD experiments. Compound 2 showed promising anti-HBV activity in vitro.     

Unexpected behavior of 6H,13H-5:12,7:14-dimethanedibenzo[d,i][1,3,6,8]tetraazecine (DMDBTA) toward phenols

A new 20-membered octaazamacrocyclic compound named 1:4,6:9,11:14,16:19-tetramethylentetrabenzo[b,g,l,q][1,4,6,9,11,14,16,19]octaazaeicocine (TTBOE) (9) has been prepared by means of in situ one-pot synthesis between the aminal 6H,13H-5:12,7:14-dimethanedibenzo[d,i][1,3,6,8]tetraazecine (DMDBTA) (3) and electron-deficient phenols. Otherwise, electron-rich phenols such as 4-chloro-3,5-dimethylphenol or 2-naphthol produce an ortho-regioselective aminomethylation resulting in 2-(1H-benzimidazol-1-ylmethyl)-4-chloro-3,5-dimethylphenol (7) and 1-(1H-benzimidazol-1-ylmethyl)-2-naphthol (8) in a Mannich type reaction in a basic medium. Moreover, obtainment of 1,1′-methylenbis(1H-benzimidazole) (15) from TTBOE is discussed.     

14-Noreudesmanes and a phenylpropane heterodimer from sea buckthorn berry inhibit Herpes simplex type 2 virus replication

Two new 14-noreudesmane sesquiterpenes, one new phenylpropane heterodimer, caulilexin C, and uvaol were isolated from the 70% MeOH extract of the fruit peel of Elaeagnus rhamnoides. The structures of the compounds were elucidated by HRESIMS and advanced NMR methods. The absolute configuration of (R)-6,9-dihydroxy-1-oxo-14-noreudesm-5,7,9-triene was determined by the TDDFT-ECD method. The new compounds, together with structurally similar naphthalenes (musizin, musizin-8-O-glucoside, torachrysone-8-O-glucoside) and 1,4-naphthoquinone (2-methylstipandrone), isolated previously from Rumex aquaticus, were investigated for their antiviral activity against Herpes simplex virus type 2 (HSV-2) using two different methods. Applying the traditional virus yield reduction test, (R)-6,9-dihydroxy-1-oxo-14-noreudesm-5,7,9-triene, 1-[3-methoxy-4-(2-methoxy-4-(1E)-propenyl-phenoxy)-phenyl]-propane-1,2-diol, and musizin caused a 2.00 log₁₀, 3.49 log₁₀, and 2.33 log₁₀ reduction of HSV-2 yield, respectively, at a concentration of 12.5?μM. 2-Hydroxy-1-methoxy-6,9-dioxo-14-noreudesm-1,3,5(10),7-tetraene exhibited an antiviral effect at concentration of 50?μM only. Similar results were obtained when the qPCR method was used to test the antiviral activity of the compounds.     

Synthesis and self-assembly of dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium derivates

A novel synthetic method toward nitrogen containing positively charged dibenzo[jk,mn]naphtho[2,1,8-fgh]thebenidinium (DBNT, 1) salts was developed. In this method, the undehydrogenated precursor of DBNT, 14-phenyl-14-dibenzo[a,j]acridinium salt (6), was produced directly from the reaction between 14-phenyl-14-dibenzo[a,j]xanthenylium (2) and amine/aniline in reasonable yield. Various DBNT salts with different alkyl and alkylphenyl chains were synthesized in this two-step method. The self-assembly behavior of two alkylated DBNT salts, 1c and 1f, was studied in this work. Due to the different substituents and counterions, compound 1c formed nanoscale wirelike fibers, and helical aggregates were obtained from 1f, in their methanolic solutions.     

Sulfamic acid: a novel and efficient catalyst for the synthesis of aryl-14H-dibenzo[a.j]xanthenes under conventional heating and microwave irradiation

A simple and convenient procedure for the synthesis of aryl-14H-dibenzo[a.j]xanthenes is described through a one-pot condensation of β-naphthol with aryl aldehydes in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.     

Rare earth metal-rich indides RE14Rh3−xIn3 (RE=Y, Dy, Ho, Er, Tm, Lu)

The rare earth (RE) metal-rich indides RE₁₄Rh_3-xIn₃ (RE=Y, Dy, Ho, Er, Tm, Lu) can be synthesized from the elements by arc-melting or induction melting in tantalum crucibles. They were investigated by X-ray diffraction on powders and single crystals: Lu₁₄Co₃In₃ type, space group P4₂/nmc, Z=4, a=961.7(1), c=2335.5(5) pm, wR2=0.052, 2047 F² values, 62 variables for Y₁₄Rh₃In₃, a=956.8(1), c=2322.5(5) pm, wR2=0.068, 1730 F² values, 63 variables for Dy₁₄Rh_2.89(1)In₃, a=952.4(1), c=2309.2(5) pm, wR2=0.041, 1706 F² values, 63 variables for Ho₁₄Rh_2.85(1)In₃, a=948.6(1), c=2302.8(5) pm, wR2=0.053, 1977 F² values, 63 variables for Er₁₄Rh_2.86(1)In₃, a=943.8(1), c=2291.5(5) pm, wR2=0.065, 1936 F² values, 63 variables for Tm₁₄Rh_2.89(1)In₃, and a=937.8(1), c=2276.5(5) pm, wR2=0.050, 1637 F² values, 63 variables for Lu₁₄Rh_2.74(1)In₃. Except Yb₁₄Rh₃In₃, the 8g Rh1 sites show small defects. Striking structural motifs are rhodium-centered trigonal prisms formed by the RE atoms with comparatively short Rh-RE distances (271-284 pm in Y₁₄Rh₃In₃). These prisms are condensed via common corners and edges building two-dimensional polyhedral units. Both crystallographically independent indium sites show distorted icosahedral coordination. The icosahedra around In2 are interpenetrating, leading to In2-In2 pairs (309 pm in Y₁₄Rh₃In₃).     

Plectranthoic acid A & B, two new triterpenoids from Plectranthus rugosus

Two new triterpenoid acids, designated as plectranthoic acid A and plectranthoic acid B, have been isolated from P. rugosus and are characterised as (20-S)-3α-hydroxy-18α,19α-$\text{H}\text{-}$-urs-12-en-30β-oic acid and (14-S)-3α-hydroxy-18α, 19α $\text{H}\text{-}$-urs-12-en-27α-oic acid.