Synthesis and antifungal activity of 7-methyl-7-hydroxy-2,3-benzo[c]octa-1,6-olide

Design, synthesis, antifungal activity and molecular docking of novel pyrazole-4-carboxamides containing tertiary alcohol and difluoromethyl moiety as potential succinate dehydrogenase inhibitors

BACKGROUND

Resistance problems with the long-term and frequent use of existing fungicides, and the lack of structure diversity of traditional pyrazole-4-carboxamide succinate dehydrogenase inhibitors, it is highly required to design and develop new fungicides to address the resistance issue.

RESULTS

Different from previous pyrazole-4-carboxamide succinate dehydrogenase inhibitors by breaking the norm of difluoromethyl at the C-3 position of pyrazole and introducing a tertiary alcohol group at the C-3 position, 27 novel pyrazole-4-carboxamide derivatives were designed, synthesized and characterized by proton (1 H) nuclear magnetic resonance (NMR), carbon-13 (13 C) NMR, fluorine-19 (19 F) NMR and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The crystal structures of compounds A14 and C5 were analyzed by single crystal X-ray diffraction. Their in vitro antifungal activities were evaluated against phytopathogen Fusarium graminearum, Botrytis cinerea, Phytophthora capsica, Sclerotinia sclerotiorum, Thanatephorus cucumeris. The results displayed that most of them exhibited significant antifungal activities against S. sclerotiorum at 50 mg/L, the half maximal effective concentration (EC50 ) data of A8 and A14 were 3.96 and 2.52 mg/L, respectively. Their in vivo antifungal activities were evaluated against Pseudoperonospora cubensis, Puccinia sorghi Schw, Colletotrichum gloeosporioides, F. graminearum, Erysiphe graminis, Thanatephorus cucumeris, the control efficacies of A6, B3, C3, and C6 against E. graminis reached 100% at a concentration of 400 mg/L. The molecular docking results showed that the binding mode of the target compounds containing tertiary alcohols were similar to that of fluxapyroxad in succinate dehydrogenase. In addition, tertiary alcohols were involved in the formation of hydrogen bonds.

CONCLUSION

The excellent in vitro and in vivo inhibitory activities of novel pyrazole-4-carboxamide derivatives against succinate dehydrogenase were reported for the first time, and they could be used as the potential lead compounds. © 2023 Society of Chemical Industry.

Discovery of Novel Cinnamide Fungicidal Leads with Optical Hydroxyl Side Chain

In order to overcome the resistance of phytopathogens to commercial fungicides, a series of optical 2-methyl-2,3-diol-5-pentyl-based cinnamamide derivatives were rationally designed, synthesized, characterized, and evaluated for their in vitro and in vivo fungicidal activities. The bioassay results indicated that the EC50 (concentration for 50% of maximal effect) values of (R)-11f, (R)-11m, (S)-11m and (R)-11n were 0.16, 0.28, 0.41 and 0.47 µg/mL in the in vitro evaluation against Sclerotinia sclerotiorum, respectively, while compounds (R)- and (S)-11i, (R)- and (S)-11j exhibited excellent in vivo fungicidal activity against Pseudoperonspera cubensis with inhibition rates of 100% at 400 μg/mL. These findings supported the idea that optical 2-methyl-2,3-diol-5-pentyl-containing cinnamamides (R)- and (S)-11i, (R)- and (S)-11j with 2-chloro-4-trifluoromethyl aniline and 2-(4-chlorophenyl) aniline showed excellent in vivo fungicidal activity against S. sclerotiorum and P. cubensis and were promising fungicide candidates.

Synthesis, biological evaluation and molecular docking studies of indeno [1, 2-c] pyrazol derivatives as inhibitors of mitochondrial malate dehydrogenase 2 (MDH2)

Hypoxia inducible factor-1 (HIF-1) is a pivotal transcription factor, which is strongly correlated with the induction of angiogenesis, tumor survival, metastasis, and cell proliferation, making it a pivotal therapeutic target for solid tumor therapeutic agents. Herein, a new series of multi-functional chemical probes were designed including principal groups, viz. adamantyl and indene, at various locations of the parent compound LW6. Molecular docking studies were performed on the designed compounds and their relationship with HIF-1α and malate dehydrogenase 2 (MDH2). Inhibition of MDH2 by our compounds was expected to decrease the NADH level. Indeed, treatment of the breast cancer cell line 4T1 led to a strong reduction of the NADH concentration. The greatest reduction in NADH production in mitochondria was observed with (E)-3-(4-((3r, 5r, 7r)-adamantan-1-yl) phenoxy)-N-(5-(piperidine-1-carbonyl)-1, 4-dihydroindeno [1, 2-c] pyrazol-3-yl) acrylamide (18: IC₅₀ = 59 nM), and has the best inhibitory potential under hypoxic conditions (MCF-7: IC₅₀ = 57 nM). This compound also gave one of the highest docking "higher than the score obtained with LW6 in parallel (-31.63 kcal/mol) in the initial docking runs (PDB Code: 4WLO). Other related compounds with good yields were also synthesized from docking results, and all the synthesized compounds (14, 18, 22, 26, 29, 30) were evaluated in vitro on human adenocarcinoma cell lines.

Synthesis and Fungicidal Activities of (Z/E)-3,7-Dimethyl-2,6-octadienamide and Its 6,7-Epoxy Analogues

In order to find new lead compounds with high fungicidal activity, (Z/E)-3,7-dimethyl-2,6-octadienoic acids were synthesized via selective two-step oxidation using the commercially available geraniol/nerol as raw materials. Twenty-eight different (Z/E)-3,7-dimethyl-2,6-octadienamide derivatives were prepared by reactions of (Z/E)-carboxylic acid with various aromatic and aliphatic amines, followed by oxidation of peroxyacetic acid to afford their 6,7-epoxy analogues. All of the compounds were characterized by HR-ESI-MS and ¹H-NMR spectral data. The preliminary bioassays showed that some of these compounds exhibited good fungicidal activities against Rhizoctonia solani (R. solani) at a concentration of 50 µg/mL. For example, 5C, 5I and 6b had 94.0%, 93.4% and 91.5% inhibition rates against R. solani, respectively. Compound 5f displayed EC₅₀ values of 4.3 and 9.7 µM against Fusahum graminearum and R. Solani, respectively.

Synthesis of o-Carboxyarylacrylic Acids by Room Temperature Oxidative Cleavage of Hydroxynaphthalenes and Higher Aromatics with Oxone

A simple procedure for the synthesis of a variety of o-carboxyarylacrylic acids has been developed with Oxone (2KHSO5·KHSO4·K2SO4); the oxidation reaction involves the stirring of methoxy/hydroxy-substituted naphthalenes, phenanthrenes, anthracenes, etc. with Oxone in an acetonitrile-water mixture (1:1, v/v) at rt. Mechanistically, the reaction proceeds via initial oxidation of naphthalene to o-quinone, which undergoes cleavage to the corresponding o-carboxyarylacrylic acid. The higher aromatics are found to yield carboxymethyl lactones derived from the initially formed o-carboxyarylacrylic acids.

Concise stereoselective total synthesis of (+)-muricatacin and (+)-epi-muricatacin

Efficient stereoselective total synthesis of (+)-muricatacin (1) and (+)-epi-muricatacin (8) was accomplished from commercially available chemical pent-4-ynoic acid via Shi's asymmetric epoxidation and Mitsunobu reaction as the key steps in 17.8% and 26.9% overall yields, respectively.