Cu-Catalyzed Direct Enantioselective Vinylogous Mannich Reaction between ß,γ-Unsaturated Pyrazoleamides and Ketimines.

A catalytic asymmetric vinylogous Mannich-type reaction between ß,γ-unsaturated amides and ketimines has been developed in excellent regio-, diastereo-, and enantioselectivities. The methodology provides an efficient approach to construct chiral homoallylic amines with a 3-amino-2-oxindole scaffold. Moreover, the transformations of the chiral products, including the removal of the pyrazole group or Boc group, the reduction of the C-C double bond, and Suzuki coupling, have been investigated.

Aromatic Ring-Fused Dipyrrins: Programmed [4 + 2]-Cycloaddition Pathway with Regio-selectivity upon Alkylamino-Substitution.

Sulfolenodipyrrins are employed as building blocks to concisely and efficiently construct aromatic rings (e.g., naphthoquinone, anthraquinone, fullerenes, and phthalimide) from fused dipyrrins by programmed [4 + 2]-cycloaddition reactions. Notably, alkylamino-substitution at the α-position not only enhances the reactivity of sulfolenodipyrrins but also results in the regio-selectivity of the cycloaddition reactions. Theoretical calculations in terms of frontier orbitals of dienes, energy of dienes, steric hindrance, and aromaticity have been conducted to understand the reason in depth. Additionally, the fusion of aromatic groups enables bathochromic absorption with up to ∼130 nm for the monoadducts and to ∼200 nm for the bis-adducts. The phthalimide annulation dipyrrin displays red emission, while the other mono- or bis-adducts do not, owing to the presence of typical acceptors such as quinone analogs or fullerene.

[Prediction of quality markers and medicinal value of sea buckthorn leaves based on network pharmacology, content determination, and activity evaluation].

The leaves of sea buckthorn(Hippophae rhamnoides), considered as common food raw materials, have records of medicinal use and diverse pharmacological activities, showing a potential medicinal value. However, the active substances in the sea buckthorn leaves and their mechanisms of action remain unclear. In addition, due to the extensive source and large variety variations, the quality evaluation criteria of sea buckthorn leaves remain to be developed. To solve the problems, this study predicted the main active components, core targets, key pathways, and potential pharmacological effects of sea buckthorn leaves by network pharmacology and molecular docking. Furthermore, ultra-performance liquid chromatography with diode-array detection(UPLC-DAD) was employed to determine the content of active components and establish the chemical fingerprint, on the basis of which the quality markers of sea buckthorn leaves were predicted and then verified by the enzyme activity inhibition method. The results indicated that sea buckthorn leaves had potential therapeutic effects on a variety of digestive tract diseases, metabolic diseases, tumors, and autoimmune diseases, which were consistent with the ancient records and the results of modern pharmacological studies. The core targets of sea buckthorn leaves included PTPN11, AKT1, PIK3R1, ESR1, and SRC, which were mainly involved in the PI3K-AKT, MAPK, and HIF-1 signaling pathways. In conclusion, the active components of sea buckthorn leaves are associated with the rich flavonoids and tannins, among which quercitrin, narcissoside, and ellagic acid can be used as the quality markers of sea buckthorn leaves. The findings provide a reference for the quality control and further development and utilization of sea buckthorn leaves as medicinal materials.

Formal (4+2) cycloaddition of azoalkenes with trifluoromethylimidoyl sulfoxonium ylides: synthesis of trifluoromethyl pyridazine derivatives.

CF3-substituted imidoyl sulfoxonium ylides (TFISYs) are extraordinarily versatile and powerful synthons for use in cyclization chemistry that affords diverse CF3-substituted N-heterocycles. We first reacted TFISYs as a two-atom synthon with readily available azoalkenes and then subjected the products to metal-free formal (4+2) cycloaddition chemistry. This protocol features mild conditions and broad substrate scope, is simple to operate, and provides highly functionalized trifluoromethylpyridazines that are widely found in bioactive molecules.

Rhodium-Catalyzed 1,4-Aryl Rearrangement of Sulfur Ylide for the Synthesis of 2-Pyridyl Thioethers.

We report a novel rhodium-catalyzed rearrangement involving N-substituted 2-thiopyridones and diazoesters. This reaction proceeds through the rhodium-catalyzed formation of sulfur ylides, followed by a direct C-N bond cleavage to achieve N-to-C 1,4-pyridyl migration. The protocol can be used to construct various thiopyridines possessing tetrasubstituted carbon stereocenters in moderate to excellent yields, which expands the transformation pattern of sulfur ylide intermediates in rearrangement reactions.

Chain Length Modulated Dimerization and Cyclization of Terminal Thienyl-Blocked Oligopyrranes.

Oxidation of thienyl-blocked bilane and pentapyrrane afforded chain length dependent products of the symmetric dimer D1 and the thienyloligopyrrin-appended pentaphyrin analogue P2, respectively, with the latter formed by simultaneous dimerization and cyclization. Coordination of D1 and P2 with Cu(II) afforded di- and monometallic complexes D1-Cu2 and P2-Cu, respectively. These compounds exhibit distinct NIR absorption, with the absorption tail of D1-Cu2 extended to ca. 1900 nm despite its smaller conjugation framework than that of P2-Cu.

Catalytic Desymmetric Dicarbofunctionalization of Unactivated Alkenes.

The construction of multi-stereocenters by a transition metal-catalyzed cross-coupling reaction is a major challenge. The catalytic desymmetric functionalization of unactivated alkenes remains largely unexplored. Herein, we disclose -a desymmetric dicarbofunctionalization of 1,6-dienes via a nickel-catalyzed reductive cross-coupling reaction. The leverage of the underdeveloped chiral 8-Quinox enables the Ni-catalyzed desymmetric carbamoylalkylation of both unactivated mono- and disubstituted alkenes to form pyrrolidinone bearing two nonadjacent stereogenic centers in high enantio- and stereoselectivitives with broad functional-group tolerance. The synthetic application of pyrrolidinones allows the rapid access to complex chiral fused-heterocycles.

High-throughput tandem-microwell assay for ammonia repositions FDA-Approved drugs to inhibit Helicobacter pylori urease.

To date, little attempt has been made to develop new treatments for Helicobacter pylori (H. pylori), although the community is aware of the shortage of treatments for H. pylori. In this study, we developed a 192-tandem-microwell-based high-throughput assay for ammonia that is a known virulence factor of H. pylori and a product of urease. We could identify few drugs, that is, panobinostat, dacinostat, ebselen, captan, and disulfiram, to potently inhibit the activity of ureases from bacterial or plant species. These inhibitors suppress the activity of urease via substrate-competitive or covalent-allosteric mechanism, but all except captan prevent the antibiotic-resistant H. pylori strain from killing human gastric cells, with a more pronounced effect than acetohydroxamic acid, a well-known urease inhibitor and clinically used drug for the treatment of bacterial infection. This study offers several bases for the development of new treatments for urease-containing pathogens and to study the mechanism responsible for the regulation of urease activity.

Concise Synthesis of Chromene/Chromane-Type Aryne Precursors and Their Applications.

The gram-scale synthesis of 5,6-, 6,7-, and 7,8-chromene/chromane-type aryne precursors and their applications in regioselective transformation to other functional derivatives is reported. Chromene/chromane-type arynes are generated under mild conditions, which can further undergo [2 + 2], [3 + 2], and [4 + 2] cycloaddition reactions, nucleophilic addition reactions, and σ-insertion reactions to produce structurally novel substituted chromenes and chromanes. The excellent regioselectivity of the reaction is facilitated by the oxygen-containing guiding groups at the ortho-position of the triple bond, which can be removed or switched to other functional groups including alkenyl, aryl, heteroaryl, and arylamino groups.

Design of a Functional Chromene-Type Kobayashi Precursor: Gram-Scale Total Synthesis of Natural Xanthones by Highly Regioselective Aryne Annulation.

The 2,2-dimethyl-2H-chromene motif is widely found in many bioactive molecules, and is a privileged structure in the pharmaceutical arena. We have developed a concise and regioselective approach to chromenes and chromanes through an aryne-based synthetic strategy. A practical, gram-scale synthetic route to a chromene-type aryne precursor was explored. Subsequently, cyclization under mild conditions afforded tetracyclic xanthone skeletons with excellent regioselectivity. Our approach provides a concise strategy for the gram-scale synthesis of chromene-type xanthones such as 6-deoxyisojacareubin, cylindroxanthone D, staudtiixanthone D, brasilixanthone A and cudracuspixanthone O.

The prevalence of ampicillin-resistant opportunistic pathogenic bacteria undergoing selective stress of heavy metal pollutants in the Xiangjiang River, China.

The emergence of clinically relevant ß-lactam-resistant bacteria poses a serious threat to human health and presents a major challenge for medical treatment. How opportunistic pathogenic bacteria acquire antibiotic resistance and the prevalence of antibiotic-resistant opportunistic pathogenic bacteria in the environment are still unclear. In this study, we further confirmed that the selective pressure of heavy metals contributes to the increase in ampicillin-resistant opportunistic pathogens in the Xiangjiang River. Four ampicillin-resistant opportunistic pathogenic bacteria (Pseudomonas monteilii, Aeromonas hydrophila, Acinetobacter baumannii, and Staphylococcus epidermidis) were isolated on Luria-Bertani (LB) agar plates and identified by 16S rRNA sequencing. The abundance of these opportunistic pathogenic bacteria significantly increased in the sites downstream of the Xiangjiang River that were heavily influenced by metal mining activities. A microcosm experiment showed that the abundance of ß-lactam resistance genes carried by opportunistic pathogenic bacteria in the heavy metal (Cu2+ and Zn2+) treatment group was 2-10 times higher than that in the control. Moreover, heavy metals (Cu2+ and Zn2+) significantly increased the horizontal transfer of plasmids in pathogenic bacteria. Of particular interest is that heavy metals facilitated the horizontal transfer of conjugative plasmids, which may lead to the prevalence of multidrug-resistant pathogenic bacteria in the Xiangjiang River.

Enantioselective vinylogous aldol/lactonization cascade reaction between ß,γ-unsaturated amides and trifluoromethyl ketones: facile access to chiral trifluoromethyl dihydropyranones.

An efficient asymmetric vinylogous aldol/lactonization cascade reaction between ß,γ-unsaturated amides and trifluoromethyl ketones has been developed. Using a chiral cyclohexanediamine-based tertiary amine-thiourea catalyst, optically active trifluoromethyl dihydropyranones have been constructed in moderate-to-excellent yields (up to 99%) with excellent stereoselectivities (96-> 99.5% ee).

Tripyrrin-armed isosmaragdyrins: synthesis, heterodinuclear coordination, and protonation-triggered helical inversion.

Oxidative ring closure of linear oligopyrroles is one of the synthetic approaches to novel porphyrinoids with dinuclear coordination sites and helical chirality. The spatial arrangement of the pyrrolic groups of octapyrrole (P8) affected the position of the intramolecular oxidative coupling of the pyrrolic units; tripyrrin-armed isosmaragdyrin analogue (1) containing a ß,ß-linked bipyrrole moiety was synthesized regioselectively in a high yield by using FeCl3. NiII-coordination at the armed tripyrrin site of 1 allowed the formation of diastereomeric helical twisted complexes (2A and 2B) and succeeding CuII-coordination at the macrocyclic core afforded heterodinuclear NiII/CuII-complexes (3A and 3B). Each of them comprised a pair of separable enantiomers, exhibiting P- and M-helices, respectively. Notably, diastereomeric interconversion from 2A to 2B was quantitatively achieved as a consequence of helical transformation under acidic conditions.

N-Confused Phlorin-Prodigiosin Chimera: meso-Aryl Oxidation and π-Extension Triggered by Peripheral Coordination.

An N-confused phlorin isomer bearing a dipyrrin moiety at the α-position of the confused pyrrole ring (1) was synthesized. PdII and BIII coordination at the peripheral prodigiosin-like moiety of 1 afforded the corresponding complexes 2 and 3. Reflux of 2 in triethylamine (TEA) converted the meso-phenyl into the PdII -coordinating phenoxy group to afford 4. Under the same reaction conditions, TEA was linked to the α-position of the dipyrrin unit in 3 as an N,N-diethylaminovinyl group to afford 5. Furthermore, peripheral coordination of BIII in 3 and 5 improved the planarity of the phlorin macrocycle and thus facilitated the coordination of AgIII at the inner cavity to afford 3-Ag and 5-Ag, respectively. These results provide an effective approach for developing unique porphyrinoids through peripheral coordination.

Construction of indazolo[3,2-a]isoquinolines via [3 + 2] cycloaddition of benzynes.

A [3 + 2] annulation protocol for the construction of N-substituted indazolo[3,2-a]isoquinolines starting from benzynes and C,N-cyclic azomethine imines was developed. A diverse range of highly functionalized products indazolo[3,2-a]isoquinolines featuring an indazole scaffold can be easily accessed via a one-step reaction under mild conditions, and they show good anti-proliferative activity on cancer cells.

Cobalt-Catalyzed Ortho-C(sp2)-H Amidation of Benzaldehydes with Dioxazolones Using Transient Directing Groups.

An efficient and convenient cobalt-catalyzed ortho-C(sp2)-H amidation of benzaldehydes employing dioxazolones as the aminating reagent has been developed. The key feature of this protocol is the use of green and economic earth-abundant metals cobalt as the catalyst with the p-chloroaniline as the transient directing group. Further application of our approach was demonstrated by the synthesis of C1r serine protease inhibitor 45 and elastase inhibitor 49.

Copper-catalyzed enantioselective alkynylation of pyrazole-4,5-diones with terminal alkynes.

A copper-catalyzed enantioselective alkynylation between terminal alkynes and pyrazole-4,5-diones has been developed. With 2.5 mol% CuI and 3 mol% chiral ligand L15, chiral propargylic alcohols bearing a pyrazolone motif were produced in 82-99% yield and up to 98% ee. Moreover, both enantiomers of the chiral propargylic alcohols were obtained with ligands L12 and L15, respectively.

Cu(I)-Catalyzed Asymmetric Mannich Reaction of Glycine Schiff Bases to Ketimines.

A copper-catalyzed asymmetric Mannich reaction between glycine Schiff bases and ketimines has been developed. This method afforded 2-oxindole-based chiral syn-α,ß-diamino acid derivatives in high yields (89-99%) with good to excellent diastereoselectivities (≤98:2 dr) and excellent enantioselectivities (95-99% ee).

Synthesis of amino acid derivatives of 5-alkoxy-3,4-dihalo-2(5H)-furanones and their preliminary bioactivity investigation as linkers.

A series of amino acid derivatives are successfully synthesized via a metal-free C-N coupling reaction of 5-alkoxy-3,4-dihalo-2(5H)-furanones and amino acids. Their structures are well characterized with 1H NMR, 13C NMR, ESI-MS and elemental analysis. As potential linkers of the 2(5H)-furanone unit with other drug moieties containing a hydroxyl or amino group, the effect of amino acids is investigated by comparison with other 2(5H)-furanone compounds by constructing C-O/C-S bonds. The preliminary results of the biological activity assay by the MTT method on a series of cancer cell lines in vitro reveal that the introduction of amino acids basically has no toxic effect. This can lead to these 2(5H)-furanone derivatives being further well-linked with other bioactive moieties with amino or hydroxy groups as expected. Thus, the biological activity assay gives a direction for the design of bioactive 2(5H)-furanones based on these amino acid linkers.

Palladium-Catalyzed Electrochemical C-H Bromination Using NH4Br as the Brominating Reagent.

The palladium-catalyzed electrochemical C-H bromination of benzamide derivatives under divided cells is developed, in which NH4Br serves as a brominating reagent and electrolyte. The protocol avoids the use of chemical oxidants and provides an alternative method for the synthesis of aryl bromides.