Pyrido [1,2-a] Pyrimidinone Mesoionic Compounds Containing Vanillin Moiety: Design, Synthesis, Antibacterial Activity, and Mechanism

Abstract

Xanthomonas oryzae pv. oryzicola (Xoo) is a plant pathogen responsible for rice bacterial blight disease that remains challenging for prevention and cure. To discover innovative and extremely potent antibacterial agents, vanillin moiety was introduced to develop a series of novel mesoionic derivatives. Compound 15 demonstrated excellent in vitro antibacterial activity against Xoo, with a 50% effective concentration value (EC50) of 27.5 μg/mL, which was superior to that of the positive control agent thiodiazole copper (97.1 μg/mL) and comparable to that of compound “A11” (17.4 μg/mL). The greenhouse pot experiment also revealed that compound 15 had 38.5% curative and 36.8% protective efficacy against rice bacterial leaf blight in vivo at 100 μg/mL, which was higher than those of thiodiazole copper (31.2 and 32.6%, respectively) and compound “A11” (29.6 and 33.2%, respectively). Compound 15 enhanced the activities of related defense enzymes, increased chlorophyll content, and promoted the resistance of rice to bacterial infection by modulating the photosynthetic pathway. This study provides a basis for the subsequent structural modification and mechanism research of mesoionic derivatives.

Design, Synthesis, Antibacterial Activity, and Mechanism of Novel Mesoionic Compounds Based on Natural Pyrazole Isolated from an Endophytic Fungus Colletotrichum gloeosporioides

“…Based on the previous study conducted by our research group, the in vivo activity of the crude extract solution of anti-BLB was tested using the cutting leaves method with a slight modification. , The crude extract solution (30 mL) was diluted to 90 mL with Tween-80 aqueous solution (0.2%) containing DMSO. The concentration of thiodiazole copper (TC) (20% suspension agent) at 200 mg/L was used as the positive control, and Tween-80 aqueous solution (0.2%) containing DMSO was used as the blank control.…”

“…Finally, the assays were repeated thrice. The disease index was calculated according to the reported method, 18,19 and the prevention efficiency I (%) was calculated according to the following formula…”

“…Finally, the assays were repeated thrice. The disease index was calculated according to the reported method, , and the prevention efficiency I (%) was calculated according to the following formula where C represents the disease index of the blank control group and T represents the disease index of the treatment group.…”

“…Our previous research has shown that mesoionic compounds exhibit antibacterial activities against plant bacterial diseases. 18,19 In this study, endophytic fungi were isolated from Dendrobium officinale Kimura et Migo, and Colletotrichum gloeosporioides (NS7) were identified as biocontrol fungi through anti-Xoo biocontrol experiments. A mixed component with good inhibitory activity against Xoo was obtained via fermentation and separation of NS7.…”

Catalytic Photoredox C–H Arylation of 4-Oxo-4H-pyrido[1,2-a]pyrimidine-3-diazonium Tetrafluoroborates and Related Heteroaryl Diazonium Salts

“…1 H NMR (500 MHz, CDCl 3 ): δ major isomer 3b: 9.21 (dt, J = 7.2, 1.2 Hz, 6 H), 8.87 (s, 2 H), 7.76−7.67 (m, 8 H, 9 H, 3′ H), 7.41 (dd, J = 5.2, 1.1 Hz, 5′ H), 7.22 (ddd, J = 7.1, 6.1, 1.9 Hz, 7 H), 7.15 (dd, J = 5.1, 3.7 Hz, 4′ H); minor isomer 3′b: 9.21 (dt, J = 7.2, 1.2 Hz, 6 H), 8.75 (s, 2 H), 8.23 (dd, J = 3.0, 1.3 Hz, 2′ H), 7.76−7.67 (m, 8 H, 9 H), 7.63 (dd, J = 5.1, 1.3 Hz, 4′ H), 7.41 (dd, J = 5.2, 3.1 Hz, 5′ H), 7.19 (ddd, J = 7.2, 6.1, 1.6 Hz, 7 H). 13 C{ 1 H} NMR (126 MHz, CDCl 3 ): δ major isomer 3b: 155. 4, 150.1, 149.6, 135.3, 135.3, 127.7, 127.1, 126.7, 126.2, 124.1, 116.3, 112.0; minor isomer 3′b: 156.2, 151.5, 149.9, 135.7, 134.1, 127.6, 126.6, 125.9, 125.5, 123.9, 115.9, 112.5.…”