Natural hydrazine-containing compounds: Biosynthesis, isolation, biological activities and synthesis

Selective N-functionalization of Arylhydrazines with Primary Alcohols and Acids under PPh3/DDQ System

We present a PPh3/DDQ-mediated regiospecific selective N-functionalization of arylhydrazines with primary benzylic alcohols and aryl carboxylic acids for the synthesis of N1-benzyl arylhydrazines and N2-acyl arylhydrazines, respectively. This metal- and base-free approach features very short reaction times (about 10 min), broad substrate scope, good functional group tolerance, and mild reaction conditions. Furthermore, N1-benzlated products have also been successfully applied to the concise synthesis of N-substituted indoles and anticancer drug MDM2 inhibitor.

Design, bioactivity and mechanism of N'-phenyl pyridylcarbohydrazides with broad-spectrum antifungal activity

Succinate dehydrogenase inhibitors (SDHIs) as one of the fastest-growing fungicide categories for plant protection. In this study, a series of N'-phenyl pyridylcarbohydrazides as analogues of commercial SDHIs were designed and evaluated for inhibition activity on phytopathogenic fungi to search for potential novel SDHIs. The determination of antifungal activity in vitro and in vivo led to the discovery of a series of compounds with high activity and broad-spectrum property. Especially, N'-(4-fluorophenyl)picolinohydrazide (1c) and N'-(3,4-fluorophenyl)picolinohydrazide (1ae) showed 0.041-1.851 μg/mL of EC50 values on twelve fungi, superior to positive controls carbendazim and boscalid. In vivo activity, 1c at 50 μg/mL showed 61% of control efficacy at the post-treatment 9th day for the infection of P. piricola on apples, slightly smaller than 70% of carbendazim. In terms of action mechanism, 1c showed strong inhibition activity with IC50 of 0.107 μg/mL on SDH in Alternaria brassicae, superior to positive SDHI boscalid (IC50 0.182 μg/mL). Molecular docking indicated that 1c can well bind with the ubiquinone-binding region of SDH mainly by hydrogen bond, carbon hydrogen bond, π-alkyl, amide-π stacking, F-N and F-H interactions. Furthermore, scanning and transmission electron micrographs showed that 1c was able to obviously change the structure of mycelia and cell membrane. Fluorescence staining analysis showed that 1c could increase both the intracellular reactive oxygen species level and mitochondrial membrane potential. Finally, seed germination test, seedling growth test and cytotoxicity assay showed that 1c had very low toxicity to plant growth and mammalian cells. Thus, N'-phenyl pyridylcarbohydrazides especially 1c and 1ae can be considered promising fungicide alternatives for plant protection.

Desulfurdioxidative N-N Coupling of N-Arylhydroxylamines and N-Sulfinylanilines: Reaction Development and Mechanism

A highly efficient and chemoselective approach for the divergent assembling of unsymmetrical hydrazines through an unprecedented intermolecular desulfurdioxidative N-N coupling is developed. This metal free protocol employs readily accessible N-arylhydroxylamines and N-sulfinylanilines to provide highly valuable hydrazine products with good reaction yields and excellent functional group tolerance under simple conditions. Computational studies suggest that the in situ generated O-sulfenylated arylhydroxylamine intermediate undergoes a retro-[2π+2σ] cycloaddition via a stepwise diradical mechanism to form the N-N bond and release SO2.

Palladium(ii), platinum(ii), and silver(i) complexes with 3-acetylcoumarin benzoylhydrazone Schiff base: Synthesis, characterization, biomolecular interactions, cytotoxic activity, and computational studies

New Pd(ii) (C1), Pt(ii) (C2), and Ag(i) (C3) complexes derived from 3-acetylcoumarin benzoylhydrazone (HL) Schiff base were synthesized and characterized by FTIR, 1H NMR, UV-visible spectroscopies along with elemental analysis (C, H, N), magnetic, molar conductivity measurements, and DFT calculations. The obtained results suggested that the ligand had different behaviors in the complexes: mono-negative tridentate (C1) and neutral tridentate (C2) as an ONO-donor and neutral bidentate (C3) as an ON-donor. Quantum chemistry calculations were performed to validate the stability of the suggested geometries and indicated that all the complexes possess tetra-coordinated metal ions. The binding affinity of all the compounds toward calf thymus (ctDNA), yeast (tRNA), and bovine serum albumin (BSA) was evaluated by absorption/emission spectral titration studies, which revealed the intercalative binding to ctDNA and tRNA and static binding upon complex formation with BSA. Molecular insights into the binding affinity of the characterized complexes were provided through conducting molecular docking analysis. Moreover, the cytotoxic activity (in vitro) of the compounds was screened against human cancerous cell lines and a non-cancerous lung fibroblast (WI38) one using cis-platin as a reference drug. The IC50 and selective index (SI) values indicated the higher cytotoxic activity of all the metal complexes compared to their parent ligand. Among all the compounds, the complex C2 showed the highest activity. These results confirmed the improvement of the anticancer activity of the ligand by incorporating the metal ions. In addition, flow cytometry results showed that complexes C1 and C2 induced cell cycle arrest at S and G1/S, respectively.

Direct Construction of 1,4-Dihydropyridazines and Pyrazoles via Annulation of Alkyl 2-Aroyl-1-chlorocyclopropanecarboxylates

An efficient and chemodivergent synthesis of highly functionalized 1,4-dihydropyridazines and pyrazoles has been accomplished via base-promoted annulation between hydrazones and alkyl 2-aroyl-1-chlorocyclopropanecarboxylates, respectively. This transition-metal-free domino reaction proceeded rapidly under mild basic conditions, affording potentially bioactive 1,4-dihydropyridazine and pyrazole derivatives in moderate yields. The conversion of 1,4-dihydropyridazine to pyrazole was confirmed by adjusting the quantity of the base.

Bacterial Hydrazine Biosynthetic Pathways Featuring Cupin/Methionyl tRNA Synthetase-like Enzymes

Nitrogen-Nitrogen (N-N) bond-containing functional groups in natural products and synthetic drugs play significant roles in exerting biological activities. The mechanisms of N-N bond formation in natural organic molecules have garnered increasing attention over the decades. Recent advances have illuminated various enzymatic and nonenzymatic strategies, and our understanding of natural N-N bond construction is rapidly expanding. A group of didomain proteins with zinc-binding cupin/methionyl-tRNA synthetase (MetRS)-like domains, also known as hydrazine synthetases, generates amino acid-based hydrazines, which serve as key biosynthetic precursors of diverse N-N bond-containing functionalities such as hydrazone, diazo, triazene, pyrazole, and pyridazinone groups. In this review, we summarize the current knowledge on hydrazine synthetase mechanisms and the various pathways employing this unique bond-forming machinery.

Exogenous of different elicitors: proline and ornithine on Sansevieria trifasciata under particulate matter (PM) and volatile organic compounds (VOC)

Phytoremediation has become famous for removing particulate matter (PM) and volatile organic compounds (VOC) in situ. Plants for removing PM and VOC were associated with botanical biofilters to attract pollution to the plant. On the other hand, persistent pollution exposure can lower plant health and phytoremediation effectiveness; therefore, improving plant tolerance against stress is necessary. Various elicitors can enhance plant tolerance to certain stressors. This study aims to investigate different elicitors to maintain plant health and improve the use of plants in phytoremediation for PM and VOC pollution. This experiment used Sansevieria trifasciata hort. ex Prain under PM and VOC stress. Exogenous elicitors, such as proline, ornithine, and a commercial product, were applied to the leaf parts before exposure to PM and VOC stress. The initial concentrations of PM1, PM2.5, and PM10 were 300-350, 350-450, and 400-500 µg m-3, respectively, while the VOC concentration was 2.5-3.0 mg m-3. The plant was stressed for 7 days. The result indicated that ornithine 10 mM is vital in improving plant tolerance and inducing antioxidant enzymes against PM and VOC, while proline 50 mM and a commercial product could not reduce plant stress. This study suggests that ornithine might be an important metabolite to improve plant tolerance to PM and VOC.

Stereoselective synthesis of (R)- and (S)-1,2-diazetidine-3-carboxylic acid derivatives for peptidomimetics

The stereoselective synthesis of both enantiomers of N-protected 1,2-diazetidine-3-carboxylic acid (aAze) from homochiral glycidol is described. Orthogonal protection of this novel cyclic α-hydrazino acid allows for selective functionalisation at either Nγ or Nδ. This novel peptidomimetic building block was incorporated into the pseudotripeptides Gly-γaAze-Ala and Gly-δaAze-Ala.

Catalytic Enantioselective Aminative Difunctionalization of Alkenes

Enantioselective difunctionalization of alkenes offers a straightforward means for the rapid construction of enantioenriched complex molecules. Despite the tremendous efforts devoted to this field, enantioselective aminative difunctionalization remains a challenge, particularly through an electrophilic addition fashion. Herein, we report an unprecedented approach for the enantioselective aminative difunctionalization of alkenes via copper-catalyzed electrophilic addition with external azo compounds as nitrogen sources. A series of valuable cyclic hydrazine derivatives via either [3 + 2] cycloaddition or intramolecular cyclization have been achieved in high chemo-, regio-, enantio-, and diastereoselectivities. In this transformation, a wide range of functional groups, such as carboxylic acid, hydroxy, amide, sulfonamide, and aryl groups, could serve as nucleophiles. Importantly, a new cyano oxazoline chiral ligand was found to play a crucial role in the control of enantioselectivity.

Unearthing a Cryptic Biosynthetic Gene Cluster for the Piperazic Acid-Bearing Depsipeptide Diperamycin in the Ant-Dweller Streptomyces sp. CS113

Piperazic acid is a cyclic nonproteinogenic amino acid that contains a hydrazine N-N bond formed by a piperazate synthase (KtzT-like). This amino acid, found in bioactive natural products synthesized by non-ribosomal peptide synthetases (NRPSs), confers conformational constraint to peptides, an important feature for their biological activities. Genome mining of Streptomyces strains has been revealed as a strategy to identify biosynthetic gene clusters (BGCs) for potentially active compounds. Moreover, the isolation of new strains from underexplored habitats or associated with other organisms has allowed to uncover new BGCs for unknown compounds. The in-house "Carlos Sialer (CS)" strain collection consists of seventy-one Streptomyces strains isolated from the cuticle of leaf-cutting ants of the tribe Attini. Genomes from twelve of these strains have been sequenced and mined using bioinformatics tools, highlighting their potential to encode secondary metabolites. In this work, we have screened in silico those genomes, using KtzT as a hook to identify BGCs encoding piperazic acid-containing compounds. This resulted in uncovering the new BGC dpn in Streptomyces sp. CS113, which encodes the biosynthesis of the hybrid polyketide-depsipeptide diperamycin. Analysis of the diperamycin polyketide synthase (PKS) and NRPS reveals their functional similarity to those from the aurantimycin A biosynthetic pathway. Experimental proof linking the dpn BGC to its encoded compound was achieved by determining the growth conditions for the expression of the cluster and by inactivating the NRPS encoding gene dpnS2 and the piperazate synthase gene dpnZ. The identity of diperamycin was confirmed by High-Resolution Mass Spectrometry (HRMS) and Nuclear Magnetic Resonance (NMR) and by analysis of the domain composition of modules from the DpnP PKS and DpnS NRPS. The identification of the dpn BGC expands the number of BGCs that have been confirmed to encode the relatively scarcely represented BGCs for depsipeptides of the azinothricin family of compounds and will facilitate the generation of new-to-nature analogues by combinatorial biosynthesis.

Palladium-catalyzed allylation and carbonylation: access to allylhydrazones and allyl acylhydrazones

A palladium-catalyzed allylation of hydrazines with allyl alcohols and aldehydes was developed, enabling the syntheses of a series of allylhydrazones in good to excellent yields with high regioselectivity. Furthermore, the four-component tandem allylation carbonylation of hydrazines with allyl alcohols and aldehydes was established using the catalytic system, producing various allyl acylhydrazones. Additionally, the functionalized allyl acylhydrazones could be smoothly constructed with the catalytic system employing allylhydrazones as a partner. The catalytic system exhibited good functional tolerance with excellent regioselectivities and scaled-up capability, overcoming the limitations of chemoselectivity of the multicomponent transformation and poor conversion of the weak nucleophile.

Photoredox Catalytic Phosphine-Mediated Deoxygenative Hydroacylation of Azobenzenes with Carboxylic Acids

The convenient and precise preparation of N,N'-diarylhydrazides, especially from readily available raw materials, remains highly challenging. Here, a photoredox catalytic phosphine-mediated deoxygenative hydroacylation of azobenzenes with abundant and readily available carboxylic acids has been developed. With Ir[dF(CF3)ppy]2(dtbbpy)PF6 as the photocatalyst, the reactions proceeded smoothly in the presence of PPh3 under visible light irradiation, delivering various N,N'-diarylhydrazides in up to 92% yields. Mechanistic studies revealed that the reaction proceeds via photoredox catalysis and phosphoranyl-radical-mediated C-O bond cleavage of carboxylic acids.

Ligand-Promoted Iron-Catalyzed Nitrene Transfer for the Synthesis of Hydrazines and Triazanes through N-Amidation of Arylamines

Herein, we report that bulky alkylphosphines such as PtBu3 can switch the roles from actor to spectator ligands to promote the FeCl2 -catalyzed N-amidation reaction of arylamines with dioxazolones, giving hydrazides in high efficiency and chemoselectivity. Mechanistic studies indicated that the phosphine ligands could facilitate the decarboxylation of dioxazolones on the Fe center, and the hydrogen bonding interactions between the arylamines and the ligands on Fe nitrenoid intermediates might play a role in modulating the delicate interplay between the phosphine ligand, arylamine, and acyl nitrene N, favoring N-N coupling over N-P coupling. The new ligand-promoted N-amidation protocols offer a convenient way to access various challenging triazane compounds via double or sequential N-amidation of primary arylamines.

P(III)-Mediated Formal Reductive N-H Bond Insertion Reaction of Hydrazones to α-Keto Esters

A diazo-, metal-, and base-free multi-substituted hydrazone synthesis via a formal reductive N-H bond insertion reactions of hydrazones to α-keto esters has been developed. The protocol features a broad substrate scope and good functional group tolerance, providing N-H bond insertion products in moderate to excellent yields. Moreover, P(III)-mediated N-H functionalization of pharmaceutical containing hydrazone moiety was also successfully achieved.

Co(II) Acetate-Assisted Direct Synthesis of Acyl Hydrazones from Acyl Hydrazides under Mild Conditions

Acyl hydrazones are a class of synthetically important organic compounds that are recurrently in high demand for synthesis and use in various fields of chemistry and biology. We report the first Co(II) catalyzed one-component one-pot sustainable synthesis of acyl hydrazones only from acyl hydrazides under mild reaction conditions. Traditional and contemporary methodologies use two components (usually acyl hydrazides and aldehydes/ketones/alcohols/styrene) as the coupling partners. Our protocol, on the other hand, involves the in situ generation of aldehyde intermediate (detected by gas chromatography) from the acyl hydrazide, which then undergoes condensation with another molecule of the same acyl hydrazide in the same pot to yield acyl hydrazones in presence of mild base K2 CO3 and low-cost Co(OAc)2  ⋅ 4H2 O as catalyst. This method shows good functional group tolerance with good to excellent yield of products. Furthermore, some of the resulting acyl hydrazones have been used as synthetic precursors and explored in various post-synthetic modifications to afford N-heterocyclic compounds. Furthermore, photoswitchable properties of few synthesized acyl hydrazones are also explored using their E/Z isomerization around the C=N bond, as realized by high-pressure liquid chromatography (HPLC) and UV-vis spectroscopic studies.

Intermolecular Hydrazinative Halogenation of Alkenes with Potassium Halides as Nucleophilic Halogen Sources: Modular Entry to Phenelzine Derivatives

An approach for the efficient synthesis of halogenated hydrazines via acid-mediated electrophilic hydrazinative halogenation of alkenes is disclosed. This transformation proceeds with readily available diethyl azodicarboxylate as a hydrazine source and low-cost potassium halides as nucleophilic halogen sources. A series of iodinated, brominated, and chlorinated hydrazines are facilely produced with a wide range of functional groups. The obtained products are good platform molecules. They can be conveniently converted into a variety of valuable phenelzine analogues which are appealing for development of novel drugs treating depression.

In vitro characterization of nonribosomal peptide synthetase-dependent O-(2-hydrazineylideneacetyl)serine synthesis indicates a stepwise oxidation strategy to generate the α-diazo ester moiety of azaserine

Azaserine, a natural product containing a diazo group, exhibits anticancer activity. In this study, we investigated the biosynthetic pathway to azaserine. The putative azaserine biosynthetic gene (azs) cluster, which contains 21 genes, including those responsible for hydrazinoacetic acid (HAA) synthesis, was discovered using bioinformatics analysis of the Streptomyces fragilis genome. Azaserine was produced by the heterologous expression of the azs cluster in Streptomyces albus. In vitro enzyme assays using recombinant Azs proteins revealed the azaserine biosynthetic pathway as follows. AzsSPTF and carrier protein (CP) AzsQ are used to synthesize the 2-hydrazineylideneacetyl (HDA) moiety attached to AzsQ from HAA. AzsD transfers the HDA moiety to the C-terminal CP domain of AzsN. The heterocyclization (Cy) domain of the nonribosomal peptide synthetase AzsO synthesizes O-(2-hydrazineylideneacetyl)serine (HDA-Ser) attached to its CP domain from l-serine and HDA moiety-attached AzsN. The thioesterase AzsB hydrolyzes it to yield HDA-Ser, which appears to be converted to azaserine by oxidation. Bioinformatics analysis of the Cy domain of AzsO showed that it has a conserved DxxxxD motif; however, two conserved amino acid residues (Thr and Asp) important for heterocyclization are substituted for Asn. Site-directed mutagenesis of two Asp residues in the DxxxxD motif (D193 and D198) and two substituted Asn residues (N414 and N447) indicated that these four residues are important for ester bond synthesis. These results showed that the diazo ester of azasrine is synthesized by the stepwise oxidation of the HAA moiety and provided another strategy to biosynthesize the diazo group.

A Coating Based on Bioactive Compounds from Streptomyces spp. and Chitosan Oligomers to Control Botrytis cinerea Preserves the Quality and Improves the Shelf Life of Table Grapes

Botrytis cinerea is the most harmful postharvest disease of table grapes. Among the strategies that can be envisaged for its control, the use of coatings based on natural products is particularly promising. The study presented herein focuses on the assessment of the antagonistic capacity of two Streptomyces species and their culture filtrates against B. cinerea. Firstly, the secondary metabolites were characterized by gas chromatography-mass spectrometry, with N1-(4-hydroxybutyl)-N3-methylguanidine acetate and 2R,3S-9-[1,3,4-trihydroxy-2-butoxymethyl]guanine acetate as the main compounds produced by S. lavendofoliae DSM 40217; and cyclo(leucyloprolyl) and cyclo(phenylalanylprolyl) as the most abundant chemical species for S. rochei DSM 41729. Subsequently, the capacity of S. lavendofoliae DSM 40217 and S. rochei DSM 41729 to inhibit the growth of the pathogen was tested in dual culture plate assays, finding 85-90% inhibition. In agar dilution tests, their culture filtrates resulted in effective concentration values (EC₉₀) in the 246-3013 μg·mL^-1 range. Upon the formation of conjugate complexes with chitosan oligomers (COS) to improve solubility and bioavailability, a synergistic behavior was observed, resulting in lower EC₉₀ values, ranging from 201 to 953 μg·mL^-1. Ex situ tests carried out on 'Timpson' and 'Red Globe' table grapes using the conjugate complexes as coatings were found to maintain the turgor of the grapes and delay the appearance of the pathogen by 10-15 days at concentrations in the 750-1000 µg·mL^-1 range. Hence, the conjugate complexes of COS and the selected Streptomyces spp. culture filtrates may be put forward as promising protection treatments for the sustainable control of gray mold.

Not all bad: Gyromitrin has a limited distribution in the false morels as determined by a new ultra high-performance liquid chromatography method

Gyromitrin (acetaldehyde N-methyl-N-formylhydrazone) and its homologs are deadly mycotoxins produced most infamously by the lorchel (also known as false morel) Gyromitra esculenta, which is paradoxically consumed as a delicacy in some parts of the world. There is much speculation about the presence of gyromitrin in other species of the lorchel family (Discinaceae), but no studies have broadly assessed its distribution. Given the history of poisonings associated with the consumption of G. esculenta and G. ambigua, we hypothesized that gyromitrin evolved in the last common ancestor of these taxa and would be present in their descendants with adaptive loss of function in the nested truffle clade, Hydnotrya. To test this hypothesis, we developed a sensitive analytical derivatization method for the detection of gyromitrin using 2,4-dinitrobenzaldehyde as the derivatization reagent. In total, we analyzed 66 specimens for the presence of gyromitrin over 105 tests. Moreover, we sequenced the nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode) and nuc 28S rDNA to assist in species identification and to infer a supporting phylogenetic tree. We detected gyromitrin in all tested specimens from the G. esculenta group as well as G. leucoxantha. This distribution is consistent with a model of rapid evolution coupled with horizontal transfer, which is typical for secondary metabolites. We clarified that gyromitrin production in Discinaceae is both discontinuous and more limited than previously thought. Further research is required to elucidate the gyromitrin biosynthesis gene cluster and its evolutionary history in lorchels.

Synthesis and Antitrypanosomal and Mechanistic Studies of a Series of 2-Arylquinazolin-4-hydrazines: A Hydrazine Moiety as a Selective, Safe, and Specific Pharmacophore to Design Antitrypanosomal Agents Targeting NO Release

Nitric oxide (NO) represents a valuable target to design antitrypanosomal agents by its high toxicity against trypanosomatids and minimal side effects on host macrophages. The progress of NO-donors as antitrypanosomal has been restricted by the high toxicity of their agents, which usually is based on NO-heterocycles and metallic NO-complexes. Herein, we carried out the design of a new class of NO-donors based on the susceptibility of the hydrazine moiety connected to an electron-deficient ring to be reduced to the amine moiety with release of NO. Then, a series of novel 2-arylquinazolin-4-hydrazine, with the potential ability to disrupt the parasite folate metabolism, were synthesized. Their in vitro evaluation against Leishmania and Trypanosoma cruzi parasites and mechanistic aspects were investigated. The compounds displayed significant leishmanicidal activity, identifying three potential candidates, that is, 3b, 3c, and 3f, for further assays by their good antiamastigote activities against Leishmania braziliensis, low toxicity, non-mutagenicity, and good ADME profile. Against T. cruzi parasites, derivatives 3b, 3c, and 3e displayed interesting levels of activities and selectivities. Mechanistic studies revealed that the 2-arylquinazolin-4-hydrazines act as either antifolate or NO-donor agents. NMR, fluorescence, and theoretical studies supported the fact that the quinazolin-hydrazine decomposed easily in an oxidative environment via cleavage of the N-N bond to release the corresponding heterocyclic-amine and NO. Generation of NO from axenic parasites was confirmed by the Griess test. All the evidence showed the potential of hydrazine connected to the electron-deficient ring to design effective and safe NO-donors against trypanosomatids.

Copper-Catalyzed Radical Hydrazono-Phosphorylation of Alkenes

An efficient copper-catalyzed radical hydrazono-phosphorylation of alkenes with hydrazine derivatives and diarylphosphine oxides is described. The reaction provides a general and convenient method toward the synthesis of diverse β-hydrazonophosphine oxides in satisfactory yields. Based on conducted mechanistic experiments, a mechanism involving Ag-catalyzed oxidative generation of phosphinoyl radicals and subsequent addition to alkenes followed by Cu-assisted hydrazonation is proposed. Moreover, the practicability of the reaction is successfully demonstrated by its successful application on a gram scale.

Dependence on linkers' flexibility designed for benzenesulfonamides targeting discovery of novel hCA IX inhibitors as potent anticancer agents

Herein we reported the design and synthesis of two series comprising twenty-two benzenesulfonamides that integrate the s-triazine moiety. Target compounds successfully suppressed the hCA IX, with IC₅₀ ranging from 28.6 to 871 nM. Compounds 5d, 11b, 5b, and 7b were the most active analogues, which inhibited hCA IX isoform in the low nanomolar range (K_I = 28.6, 31.9, 33.4, and 36.6 nM, respectively). Furthermore, they were assessed for their cytotoxic activity against a panel of 60 cancer cell lines following US-NCI protocol. According to five-dose assay, 13c showed significant anticancer activity than 5c with GI₅₀-MID values of 25.08 and 189.01 µM, respectively. Additionally, 13c's effects on wound healing, cell cycle disruption, and apoptosis induction in NCI-H460 cancer cells were examined. Further, docking studies combined with molecular dynamic simulation showed a stable complex with high binding affinity of 5d to hCA IX, exploiting a favourable H-bond and lipophilic interactions.HIGHLIGHTSCarbonic anhydrase (CA) inhibitors comprising rigid and flexible linkers were developed.Compound 5d is the most potent CA IX inhibitor in the study (IC50: 28.6 nM).Compounds 5c and 13c displayed the greatest antiproliferative activity towards 60 cell lines.Compound 13c exposed constructive outcomes on normal cell lines, metastasis, and wound healing.Molecular docking and molecular dynamics (MDs) simulation was utilised to study binding mode.

Copper-Catalyzed Stereoselective Radical Phosphono-hydrazonation of Alkynes

A copper-catalyzed stereoselective phosphono-hydrazonation of terminal alkynes with alkyl carbazates and diarylphosphine oxides is described. This methodology provides facile access to a variety of β-hydrazonophosphine oxides in satisfactory yields. The reaction proceeds under mild conditions and exhibits good functional group tolerance. A mechanism featuring persulfate-mediated oxidative generation of phosphinoyl radicals and copper-assisted hydrazonation is proposed.

Biosynthesis of the Unusual Carbon Skeleton of Nocuolin A

Nocuolin A is a cytotoxic cyanobacterial metabolite that is proposed to be produced by enzymes of the noc biosynthetic gene cluster. Nocuolin A features a 1,2,3-oxadiazine moiety, a structural feature unique among natural products and, so far, inaccessible through organic synthesis, suggesting that novel enzymatic chemistry might be involved in its biosynthesis. This heterocycle is substituted with two alkyl chains and a 3-hydroxypropanoyl moiety. We report here our efforts to elucidate the origin of the carbon skeleton of nocuolin A. Supplementation of cyanobacterial cultures with stable isotope-labeled fatty acids revealed that the central C13 chain is assembled from two medium-chain fatty acids, hexanoic and octanoic acids. Using biochemical assays, we show that a fatty acyl-AMP ligase, NocH, activates both fatty acids as acyl adenylates, which are loaded onto an acyl carrier protein domain and undergo a nondecarboxylative Claisen condensation catalyzed by the ketosynthase NocG. This enzyme is part of a phylogenetically well-defined clade within similar genomic contexts. NocG presents a unique combination of characteristics found in other ketosynthases, namely in terms of substrate specificity and reactivity. Further supplementation experiments indicate that the 3-hydroxypropanoyl moiety of 1 originates from methionine, through an as-yet-uncharacterized mechanism. This work provides ample biochemical evidence connecting the putative noc biosynthetic gene cluster to nocuolin A and identifies the origin of all its carbon atoms, setting the stage for elucidation of its unusual biosynthetic chemistry.

New azodyrecins identified by a genome mining-directed reactivity-based screening

Only a few azoxy natural products have been identified despite their intriguing biological activities. Azodyrecins D–G, four new analogs of aliphatic azoxides, were identified from two Streptomyces species by a reactivity-based screening that targets azoxy bonds. A biological activity evaluation demonstrated that the double bond in the alkyl side chain is important for the cytotoxicity of azodyrecins. An in vitro assay elucidated the tailoring step of azodyrecin biosynthesis, which is mediated by the S-adenosylmethionine (SAM)-dependent methyltransferase Ady1. This study paves the way for the targeted isolation of aliphatic azoxy natural products through a genome-mining approach and further investigations of their biosynthetic mechanisms.

A Natural Dihydropyridazinone Scaffold Generated from a Unique Substrate for a Hydrazine-Forming Enzyme

Nitrogen-nitrogen bond-containing functional groups are rare, but they are found in a considerably wide class of natural products. Recent clarifications of the biosynthetic routes for such functional groups shed light onto overlooked biosynthetic genes distributed across the bacterial kingdom, highlighting the presence of yet-to-be identified natural products with peculiar functional groups. Here, the genome-mining approach targeting a unique hydrazine-forming gene led to the discovery of actinopyridazinones A (1) and B (2), the first natural products with dihydropyridazinone rings. The structure of actinopyridazinone A was unambiguously established by total synthesis. Biosynthetic studies unveiled the structural diversity of natural hydrazines derived from this family of N-N bond-forming enzymes.

Surprising Chemistry of 6-Azidotetrazolo[5,1-a]phthalazine: What a Purported Natural Product Reveals about the Polymorphism of Explosives

6-Azidotetrazolo[5,1-a]phthalazine (ATPH) is a nitrogen-rich compound of surprisingly broad interest. It is purported to be a natural product, yet it is closely related to substances developed as explosives and is highly polymorphic despite having a nearly planar structure with little flexibility. Seven solid forms of ATPH have been characterized by single-crystal X-ray diffraction. The structures show diverse patterns of molecular organization, including both stacked sheets and herringbone packing. In all cases, N···N and C-H···N interactions play key roles in ensuring molecular cohesion. The high polymorphism of ATPH appears to arise in part from the ability of virtually every atom of nitrogen and hydrogen in the molecule to take part in close N···N and C-H···N contacts. As a result, adjacent molecules can adopt many different relative orientations that are energetically similar, thereby generating a polymorphic landscape with an unusually high density of potential structures. This landscape has been explored in detail by the computational prediction of crystal structures. Studying ATPH has provided insights into the field of energetic materials, where access to multiple polymorphs can be used to improve performance and clarify how it depends on molecular packing. In addition, our work with ATPH shows how valuable insights into molecular crystallization, often gleaned from statistical analyses of structural databases, can also come from in-depth empirical and theoretical studies of single compounds that show distinctive behavior.

A pH-applicative fluorescent probe with long measuring range for monitoring hydrazine in water samples and Arabidopsis thaliana

In this work, a fluorescent probe, RhodCl-Hz, with pH-applicative capability and long measuring range, was developed to serve the topic on the enrichment process of hydrazine. It was practical due to the clear acid-base boundary and the sectioned linear ranges. With the excitation wavelength of 515 nm and the emission peak at 565 nm, the detecting system was steady. It exhibited a clear cut-off point at pH 7.0 and steady fluorescence signals within the range of 7.0-10.0. As a whole, the linear range of 10.0-500 µM (1.0-50.0 equivalent) was long. The Limit of Detection value was calculated as 0.64 μM. With high selectivity, RhodCl-Hz was applied to suit water samples and biological imaging in both Arabidopsis Thaliana root tips and living MCF-7 cells. The information here might be helpful for revealing the enrichment process of hydrazine.

Efficiently enantioselective synthesis of pyrazolines and isoxazolines enabled by iridium-catalyzed intramolecular allylic substitution reactions

An efficient Ir-catalyzed enantioselective intramolecular allylic substitution reaction of 2-tosylhydrazono or hydroxyimino carbonates for the synthesis of pyrazolines and isoxazolines has been achieved. The products were obtained in high yield...

Synthesis and Computationally Assisted Spectroscopic Study of Tautomerism in 3-(Phenyl(2-arylhydrazineylidene)methyl)quinoxalin-2(1H)-ones

The recently developed efficient protocol combining implicit and explicit, accurate quantum mechanical modeling of the condensed state [Katsyuba et al., J. Chem. Phys. 155, 024507 (2021)] is used to describe...

Quinoline–hydrazone hybrids as dual mutant EGFR inhibitors with promising metallic nanoparticle loading: rationalized design, synthesis, biological investigation and computational studies

A novel quinoline–hydrazone hybrid induced apoptosis in MCF-7 cells through dual mutant EGFR inhibition with promising metallic nanoparticle loading.

Biosynthesis of triacsin featuring an N-hydroxytriazene pharmacophore

Triacsins are an intriguing class of specialized metabolites possessing a conserved N-hydroxytriazene moiety not found in any other known natural products. Triacsins are notable as potent acyl-CoA synthetase inhibitors in lipid metabolism, yet their biosynthesis has remained elusive. Through extensive mutagenesis and biochemical studies, we here report all enzymes required to construct and install the N-hydroxytriazene pharmacophore of triacsins. Two distinct ATP-dependent enzymes were revealed to catalyze the two consecutive N-N bond formation reactions, including a glycine-utilizing, hydrazine-forming enzyme (Tri28) and a nitrite-utilizing, N-nitrosating enzyme (Tri17). This study paves the way for future mechanistic interrogation and biocatalytic application of enzymes for N-N bond formation.

Non-enzymatic Transformation of Aflatoxin B1 by Pseudomonas geniculata m29

Aflatoxin B₁ (AFB₁) is the most harmful mycotoxin produced by filamentous fungi and presents a serious threat to human and animal health. Therefore, it is essential to protect humans and animals from AFB₁-induced acute and chronic toxicity. In this study, Pseudomonas strain m29 having a high efficiency of AFB₁ transformation was isolated from soil. The transformation ratio by m29 was more than 97% within 24 h, and the optimum temperature for transformation was 37°C. Moreover, the AFB₁ transforming activity was mainly attributed to the cell-free supernatant of strain m29. The metabolite that plays a crucial role in AFB₁ transformation is likely 1,2-dimethylhydrazine or 1,1-dimethylhydrazine, as identified by GC-MS and LC-MS analysis. AFB₁ was transformed into a product with molecular formula C₁₇H₁₄O₇. To the best of our knowledge, this is the first study of non-enzymatic AFB₁ transformation by bacteria. Importantly, this AFB₁ transformation mechanism could be universal to various microorganisms.

Role of Hydrazine-Related Chemicals in Cancer and Neurodegenerative Disease

Hydrazine-related chemicals (HRCs) with carcinogenic and neurotoxic potential are found in certain mushrooms and plants used for food and in products employed in various industries, including aerospace. Their propensity to induce DNA damage (mostly O⁶-, N⁷- and 8-oxo-guanine lesions) resulting in multiple downstream effects is linked with both cancer and neurological disease. For cycling cells, unrepaired DNA damage leads to mutation and uncontrolled mitosis. By contrast, postmitotic neurons attempt to re-enter the cell cycle but undergo apoptosis or nonapoptotic cell death. Biomarkers of exposure to HRCs can be used to explore whether these substances are risk factors for sporadic amyotrophic laterals sclerosis and other noninherited neurodegenerative diseases, which is the focus of this paper.

Crystal structure and mol-ecular docking study of (E)-2-{[(E)-2-hy-droxy-5-methyl-benzyl-idene]hydrazinyl-idene}-1,2-di-phenyl-ethan-1-one

The title compound, C22H18N2O2, is a Schiff base that exists in the phenol-imine tautomeric form and adopts an E configuration with respect to the C=N bond. The mol-ecular structure is stabilized by an O-H⋯N hydrogen bond, forming an S(6) ring motif. In the crystal, pairs of C-H⋯O hydrogen bonds link the mol-ecules to form inversion dimers. Weak π-π stacking inter-actions along the a-axis direction provide additional stabilization of the crystal structure. The mol-ecule is non-planar, the aromatic ring of the benzaldehyde residue being nearly perpendicular to the phenyl and 4-methyl-phenol rings with dihedral angles of 88.78 (13) and 82.26 (14)°, respectively. A mol-ecular docking study between the title mol-ecule and the COVID-19 main protease (PDB ID: 6LU7) was performed, showing that it is a potential agent because of its affinity and ability to adhere to the active sites of the protein.

Evidence of an nN(amide) → π*Ar Interaction in N-Alkyl-N,N'-diacylhydrazines

1,2-Dibenzoyl-1-tert-butylhydrazine (RH-5849) and related N-alkyl-N,N'-diacylhydrazines are environmentally benign insect growth regulators. Herein, we show that an unusual n_N(amide) → π*_Ar interaction mediated by a hydrazide amide nitrogen atom plays a crucial role in stabilizing their biologically active trans-cis (t-c) rotameric conformations. We provide NMR and IR spectroscopic evidence for the presence of these interactions, which is also supported by X-ray crystallographic and computational studies.

Complete Biosynthetic Pathway of Alazopeptin, a Tripeptide Consisting of Two Molecules of 6-Diazo-5-oxo-l-norleucine and One Molecule of Alanine

DON (6-diazo-5-oxo-l-norleucine), a diazo-containing amino acid, has been studied for more than 60 years as a potent antitumor agent, but its biosynthesis has not been elucidated. Here we reveal the complete biosynthetic pathway of alazopeptin, the tripeptide Ala-DON-DON, which has antitumor activity, by gene inactivation and in vitro analysis of recombinant enzymes. We also established heterologous production of N-acetyl-DON in Streptomyces albus. DON is synthesized from lysine by three enzymes and converted to alazopeptin by five enzymes and one carrier protein. Most interestingly, transmembrane protein AzpL was indicated to catalyze diazotization using 5-oxolysine and nitrous acid as substrates. Site-directed mutagenesis of AzpL indicated that the hydroxy group of Tyr-93 is important for the diazotization. These findings expand our knowledge of the enzymology of N-N bond formation.

Nitrogen-Nitrogen Bond Formation Reactions Involved in Natural Product Biosynthesis

Construction of nitrogen-nitrogen bonds involves sophisticated biosynthetic mechanisms to overcome the difficulties inherent to the nucleophilic nitrogen atom of amine. Over the past decade, a multitude of reactions responsible for nitrogen-nitrogen bond formation in natural product biosynthesis have been uncovered. On the basis of the intrinsic properties of these reactions, this Review classifies these reactions into three categories: comproportionation, rearrangement, and radical recombination reactions. To expound the metallobiochemistry underlying nitrogen-nitrogen bond formation reactions, we discuss the enzymatic mechanisms in comparison to well characterized canonical heme-dependent enzymes, mononuclear nonheme iron-dependent enzymes, and nonheme di-iron enzymes. We also illuminate the intermediary properties of nitrogen oxide species NO₂^-, NO⁺, and N₂O₃ in nitrogen-nitrogen bond formation reactions with clues derived from inorganic nitrogen metabolism driven by anammox bacteria and nitrifying bacteria. These multidimentional discussions will provide further insights into the mechanistic proposals of nitrogen-nitrogen bond formation in natural product biosynthesis.

Mechanism-Based Inactivation of Cytochrome P450 Enzymes: Computational Insights

Mechanism-based inactivation (MBI) refers to the metabolic bioactivation of a xenobiotic by cytochrome P450s to a highly reactive intermediate which subsequently binds to the enzyme and leads to the quasi-irreversible or irreversible inhibition. Xenobiotics, mainly drugs with specific functional units, are the major sources of MBI. Two possible consequences of MBI by medicinal compounds are drug-drug interaction and severe toxicity that are observed and highlighted by clinical experiments. Today almost all of these latent functional groups (e.g., thiophene, furan, alkylamines, etc.) are known, and their features and mechanisms of action, owing to the vast experimental and theoretical studies, are determined. In the past decade, molecular modeling techniques, mostly density functional theory, have revealed the most feasible mechanism that a drug undergoes by P450 enzymes to generate a highly reactive intermediate. In this review, we provide a comprehensive and detailed picture of computational advances toward the elucidation of the activation mechanisms of various known groups with MBI activity. To this aim, we briefly describe the computational concepts to carry out and analyze the mechanistic investigations, and then, we summarize the studies on compounds with known inhibition activity including thiophene, furan, alkylamines, terminal acetylene, etc. This study can be reference literature for both theoretical and experimental (bio)chemists in several different fields including rational drug design, the process of toxicity prevention, and the discovery of novel inhibitors and catalysts.