One-pot catalyst-free synthesis of benzopyrroxazine derivatives by a mutually activated sequential annulation process.

A one-pot catalyst-free reaction of o-hydroxyaryl azomethine ylides, vinyl pyridines and paraformaldehyde for the synthesis of benzopyrroxazines is reported, which offers a straightforward and atom-economical procedure for the preparation of benzopyrroxazine derivatives in moderate to excellent yields under mild conditions. A self-catalyzed [3 + 2] annulation through a mutual activation method and a sequential non-catalyzed [5 + 1] annulation process contribute to this strategy. The corresponding control experiments have been conducted to reveal the mechanism of this reaction.

Two novel polyketones from the leaves and twigs of Clerodendrum trichotomum.

Two novel polyketones, along with four known compounds, were isolated from the leaves and twigs of Clerodendrum trichotomum. Their structures were determined to be clerodendruketone A (1), clerodendruketone B (2), ecdysanols E (3), ecdysanols D (4), 5,5'-dimethoxy-7-oxolariciresinol (5), and (-)-(7'S,8S,8'R)-4,4'-dihydroxy-3,3',5,5'-tetramethoxy-7',9-epoxy-lignan-9'-ol-7-one (6) through the methods of NMR, HRESIMS and ECD data analyses. The antioxidant effects against free radical were tested by DPPH assay. The antibacterial activity against Escherichia coli and Staphylococcus aureus were tested by turbidimetry assay. The results demonstrated that compounds 1 and 2 had significative antibacterial activity, and compound 3 had moderate antioxidant activity.

Study on corrosion behavior of X80 steel under stripping coating by sulfate reducing bacteria.

BACKGROUND: At present, microorganism has been considered as important factors that threaten to buried pipelines with disbonded coatings. Aiming at the problem of unknown corrosion mechanism of sulfate-reducing bacteria (SRB), a series of studies have been carried out in this paper. Spectrophotometer and fluorescent labeling technology are used to study the growth and attachment of SRB in the simulated soil solution. The corrosion behavior of X80 pipeline steel with or without SRB was researched by electrochemical methods such as open circuit potential, dynamic potential polarization curve, and electrochemical impedance spectroscopy. The microscopic morphology of the corrosion products on the surface was observed with a scanning electron microscope (SEM), and the element content of the corrosion products on the surface of the sample after corrosion was observed using X-ray energy spectrum (EDS) analysis. RESULTS: The results showed that the growth and reproduction of SRB caused the pH of the soil simulated solution to increase, which may promote the corrosion of X80 steel. In addition, the cathode reaction of X80 steel in a sterile environment is the reduction of H+, and the main corrosion product is iron oxide. When the soil simulation solution contains SRB, the cathodic reaction is controlled by both H+ reduction and sulfide depolarization reactions, and FeS appears in the corrosion products. CONCLUSION: Although the life cycle of SRB is only about 14 days, the corrosion of X80 steel is greatly promoted by SRB, and even causes corrosion perforation, which will bring huge economic losses and serious safety hazards.

Euphorfistrines A-G, cytotoxic and AChE inhibiting triterpenoids from the roots of Euphorbia fischeriana.

Seven new triterpenoids including two cycloartanes (1-2), a lanostane (3), a tirucallane (4), a dammarane (5), an ursane (6), and an oleanane (7), along with nineteen known triterpenoids (8-26), have been obtained from the roots of Euphorbia fischeriana. Their structures were established by NMR, HRESIMS, single-crystal X-ray diffraction analysis, Mosher's method, NMR calculations, ECD analysis, and comparison with structurally related known analogues. Among them, compounds 1 and 8 were a pair of cycloartane-type triterpenoids epimers. Our bioassays have established that compounds 1-5 and 10 displayed moderate cytotoxic effects, and the structure-activity relationships of cycloartane-type triterpenoids (CTTs) were further examined. Notably, some triterpenoids displayed moderate inhibitory effects against AChE by an in vitro screened experiment. Triterpenoid 7 (Euphorfistrine G, ETG) displayed the potent inhibitory effect with IC50 = 2.45 and Ki = 2.30 µM (inhibition kinetic). And, in silico docking analyses have been performed to investigate the inhibitory mechanism of compound 7.

Highly Efficient and Diastereoselective Construction of Trifluoromethyl-Containing Spiro[pyrrolidin-3,2'-oxindole] by a Catalyst-free Mutually Activated [3+2] Cycloaddition Reaction.

A catalyst-free self-catalyzed [3+2] cycloaddition reaction of isatin-derived α-(trifluoromethyl)imines with vinylpyridines is reported. The reaction offers a straightforward and atom-economical procedure for the preparation of a series of 5'-trifluoromethyl-spiro[pyrrolidin-3,2'-oxindoles] in excellent yields and diastereoselectivities. The reaction mechanism has been investigated by control experiments, DFT calculation of pKa values and the kinetic profiles, revealing that this reaction featured the mutual activation between isatin-derived α-(trifluoromethyl)imines and vinylpyridine to generate the reactive species.

Electronic halocyclization and radical haloazidation of benzene-linked 1,7-dienes for the synthesis of functionalized 3,1-benzoxazines.

A novel electronic halocyclization and radical haloazidation of benzene-linked 1,7-dienes for the formation of functionalized 3,1-benzoxazines has been achieved by using TMSN3 as an azido source and NBS as a halogen source. This methodology is highlighted by its mild conditions and wide substrate scope, which concomitantly introduces one C-N and two C-halogen bonds into one molecule.

Enantioselective Synthesis of Isoquinolines: Merging Chiral-Phosphine and Gold Catalysis.

The highly enantioselective synthesis of dihydroisoquinoline derivatives from aromatic sulfonated imines tethered with an alkyne moiety, through a one-pot asymmetric relay catalysis of chiral-phosphine and gold catalysts, is reported. Enantiomerically enriched dihydroisoquinoline derivatives were afforded in good yields and good-to-excellent ee values under mild conditions, based on the asymmetric aza-Morita-Baylis-Hillman reaction. Dihydroisoquinoline derivatives containing two chiral centers were also synthesized through further transformations.

Euphorfinoids A and B, a pair of ent-atisane diterpenoid epimers from the roots of Euphorbia fischeriana, and their bioactivities.

Euphorfinoids A and B (1 and 2), a pair of ent-atisane diterpenoid epimers with a vicinal 2,3-diol moiety, together with four known analogues (3-6), were isolated from the roots of wild Euphorbia fischeriana. Their structures were elucidated by spectroscopic analysis, including extensive NMR, HR-ESIMS, NMR calculations, X-ray diffraction, and comparison with structurally related known analogues. Our bioassays have established that compound 1 displayed moderate anti-proliferative effects on Hcc1806 cell line with IC50 15.53 ± 0.21 µM, and compound 5 showed remarkable inhibitory effects against AChE with IC50 32.56 ± 2.74 µM by an in vitro screened experiment.

Diastereoselective Synthesis of Chromeno[3,2-d]isoxazoles via Brønsted Acid Catalyzed Tandem 1,6-Addition/Double Annulations of o-Hydroxyl Propargylic Alcohols.

A Brønsted acid catalyzed tandem process to access densely functionalized chromeno[3,2-d]isoxazoles with good to excellent yields and diastereoselectivities was disclosed. The procedure is proposed to involve a 1,6-conjugate addition/electrophilic addition/double annulations process of alkynyl o-quinone methides (o-AQMs) in situ generated from o-hydroxyl propargylic alcohols with nitrones. Mild conditions, good functional group compatibility, easy scale-up of the reaction, and further product transformation demonstrated its potential application.

Six novel lignanoids with complex structures from Sigesbeckia glabrescens Makino with their cytotoxic activities.

Six new lignanoids, Glalignin A-E (1-5) and Glaneolignin A (6), together with four analogues, (+)-isolariciresinol (7), (+)-syringaresinol (8), dihydrodehydrodiconiferyl alcohol (9) and tribulusamide A (10), were obtained from the aerial parts of Sigesbeckia glabrescens Makino and also isolated for the first time from the Sigesbeckia genus. The structures of these compounds were elucidated by the interpretation of HRESIMS, 1D NMR, 2D NMR data and chemical evidence. The cytotoxic activities of the compounds were evaluated by testing their inhibition in several tumor cells using the MTT assay. New compound 2 and 5 displayed cytotoxicity against the human cancer cell lines human lung adenocarcinoma cells (A549) with IC50 values of 32.89 ± 6.83 and 35.86 ± 6.83 µM.

Euphorfinoids E-L: Diterpenoids from the roots of Euphorbia fischeriana with acetylcholinesterase inhibitory activity.

Eight undescribed diterpenoids, euphorfinoids E-L, together with twelve known analogues, were isolated from the roots of wild Euphorbia fischeriana. Their structures and absolute configurations were elucidated by a combination of NMR, MS, ECD, and X-ray diffraction analyses. The plausible biosynthetic pathway of 1 was also proposed. The isolated compounds displayed moderate inhibitory activity against acetylcholinesterase (AChE) with 50% inhibiting concentration (IC50) values of 6.23-192.38 µM.

PPh3-Catalyzed [3 + 2] Spiroannulation of 1C,3N-Bisnucleophiles Derived from Secondary ß-Ketoamides with δ-Acetoxy Allenoate: A Route to Functionalized Spiro N-Heterocyclic Derivatives.

A [3 + 2] annulation of α-substituted secondary ß-ketoamides with δ-acetoxy-modified allenoate has been developed in the presence of phosphine catalyst. In this spiroannulation reaction, ß-ketoamides were used as the bis-nucleophilic partner while the γ,δ-carbon of 5-acetoxypenta-2,3-dienoate participated as a C2 synthon, affording the desired functionalized five-membered N-heterocyclic derivatives in moderate to excellent yields and diastereoselectivities under mild conditions. Preliminary attempts on the asymmetric variant of this reaction have been also examined, giving the corresponding products with moderate ee values.

Gold(i) catalyzed tandem cyclization of propargylic esters to 4-acyloxy-1,2-dihydroquinolines.

An effective synthetic protocol for structurally diverse 4-acyloxy-1,2-dihydroquinoline compounds has been accomplished by a gold(i)-catalyzed tandem [3,3]-rearrangement and intramolecular hydroamination of propargylic esters, affording the desired products in good yields. Moreover, the asymmetric variant of this cyclization has also been achieved using a chiral nitrogen acyclic carbene (NAC) gold(i) complex. These products have application in the enantioselective synthesis of an aromatase inhibitor within three simple steps.