Glycosides from the leaves of Fraxinus Hubeiensis.

Fraxinus hubeiensis is a plant endemic to China and widely used as folk medicine to treat various diseases. However, its chemical constituents have never been reported sufficiently. Thus, the primary objective of this study was to investigate the phytochemical constituents and biological activities of F. hubeiensis leaves. Hence, combined column chromatographic and spectroscopic techniques were used to identify and characterize the secondary metabolites such as a pair of 3-keto-glycoside epimers (1) and (2), along with five known compounds (3 ~ 7). The results of α-glucosidase inhibitory activity exhibited that 1 and 2 had moderate activity with IC50 values of 359.50 and 468.43 µM, respectively, compared to a positive control acarbose with the IC50 value of 164.08 µM. However, Compounds 1-6 were shown to be inactive against the tested microbes.

Synthesis and fungicidal activity of phenazine-1-carboxylic triazole derivatives.

A total of 15 novel-substituted 3-(benzylsulfanyl)-1H-1,2,4-triazol-5-ylamine and 10 novel-substituted 3-benzylmercapto-1,2,4-triazol derivatives were synthesized based on the natural product phenazine-1-carboxylic acid (PCA). Their structures were confirmed by 1H-NMR, 13C-NMR, HRMS, and X-ray. Most substituted 3-benzylmercapto-1,2,4-triazol derivatives displayed very strong fungicidal activity against one or multiple plant pathogens in vitro and in vivo. Compounds 8b, 8h, and 8i showed a broad spectrum of fungicidal activity. Further field experiments indicated that compounds 8b, 8c, and 8h displayed better efficacy against rice blast (Pyricularia oryzae) than PCA. These data demonstrate that compounds 8b, 8c, and 8h are promising fungicidal candidates, deserving further studies.[Formula: see text].

Chemical Constituents from Fraxinus hupehensis and Their Antifungal and Herbicidal Activities.

The phytochemical investigation of Fraxinus hupehensis led to the isolation and characterization of ten compounds which were identified as fraxin (1), fraxetin (2), esculetin (3), cichoriin (4), euphorbetin (5), kaempferol-3-O-ß-rutinoside (6), oleuropein (7), linoleic acid (8), methyl linoleate (9), and ß-sitosterol (10). Structures of the isolated constituents were characterized by 1H NMR, 13C NMR and HRMS. All the compounds, except compounds 3 and 4, were isolated for the first time from this plant. Further, this was the first report for the occurrence of compound 5 in the Fraxinus species. Antifungal activity evaluation showed that compound 2 exhibited significant inhibitory effects against Bipolaris maydis, Sclerotium rolfsii, and Alternaria solani with EC50 values of 0.31 ± 0.01 mmol/L, 10.50 ± 0.02 mmol/L, and 0.40 ± 0.02 mmol/L respectively, compared to the positive control, Carbendazim, with its EC50 values of 0.74 ± 0.01 mmol/L, 1.78 ± 0.01 mmol/L and 1.41 ± 0.00 mmol/L. Herbicidal activity tests showed that compounds 8-10 had strong inhibitory effects against the roots of Echinochloa crus-galli with EC50 values of 1.16 ± 0.23 mmol/L, 1.28 ± 0.58 mmol/L and 1.33 ± 0.35 mmol/L respectively, more potently active than that of the positive control, Cyanazine, with its EC50 values of 1.56 ± 0.44 mmol/L. However, none of the compounds proved to be active against the tested bacteria (Erwinia carotovora, Pseudomonas syringae, and Ralstonia solanacearum).

Synthesis and antifungal evaluation of PCA amide analogues.

To improve the physical and chemical properties of phenazine-1-carboxylic acid (PCA) and find higher antifungal compounds, a series of PCA amide analogues were designed and synthesized and their structures were confirmed by 1H NMR, HRMS, and X-ray. Most compounds showed some antifungal activities in vitro. Particularly, compound 3d exhibited inhibition effect against Pyriculariaoryzac Cavgra with EC50 value of 28.7 µM and compound 3q exhibited effect against Rhizoctonia solani with EC50 value of 24.5 µM, more potently active than that of the positive control PCA with its EC50 values of 37.3 µM (Pyriculariaoryzac Cavgra) and 33.2 µM (Rhizoctonia solani), respectively.

A dehydrogenative cross-coupling reaction between aromatic aldehydes or ketones and dialkyl H-phosphonates for formyl or acylphenylphosphonates.

A novel DCC reaction between aromatic aldehydes or ketones and H-phosphonates has been developed for the synthesis of p-formyl or p-acylphenylphosphonates. The synthetic method has excellent para regioselectivities, good yields, and broad substrate scopes and is more benign to the environment. The DCC reaction also tolerates many functional groups, and results in a series of new p-formyl and p-acylphenylphosphonates, which should be important building blocks for the synthesis of versatile arylphosphonate derivatives.