Rapid production of prawn (Litopenaeus vannamei) under artificial pressure can result in a series of obvious challenges and is vulnerable to serious losses related to aquatic environmental issues and the unrestrained outbreak of white spot syndrome (WSS). However, to date, there are no therapeutic strategies to contain the spread of the virus. Here, we synthesized 27 coumarin derivatives and evaluated their anti-white spot syndrome virus (WSSV) activity in L. vannamei larvae. We demonstrated that electron-withdrawing and electron-giving substituent groups play an important role in reducing toxicity and WSSV replication, respectively. Two coumarin C2 (2-amino-5-oxo-4-(p-tolyl)-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile) and C7 (2-amino-4-(4-chlorophenyl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile) were regarded as the most promising anti-WSSV compounds with maximum antiviral response <5% and median effective concentration <10 mg/L. The mortality of WSSV-infected larvae decreased by more than 60% after exposure to C2 and C7. With continuous immersion of C2 and C7 exchange, the mortality further decreased to 40% at 120 h. Additionally, C2 and C7 are the relatively stable in aquacultural water, making these agents suitable for use in inhibiting WSSV horizontal transmission in static aquaculture systems. These results showed the marked advantages of using C2 and C7 in the shrimp industry, and suggest that they hold potential for the treatment and prevention of WSSV infection in shrimp seedling culture.
Diversely functionalized chromeno-pyrimidine-2,5-dione/thione compounds were synthesized by cyclocondensation of 4-hydroxy coumarin, aldehydes and urea/thiourea using tannic acid as a green catalyst and 1:1 (EtOH:H2O) as a green solvent. Different acids were screened for their catalytic activity of chromeno-pyrimidine-2,5-dione/thione derivatives. Tannic acid (10 mol%) was used as a suitable catalyst with increased catalytic activity. By utilizing this protocol, chromeno-pyrimidine scaffolds were prepared in acceptable to excellent yield without the use of conventional volatile organic solvent and toxic metal catalyst. To our best of knowledge, this is the first report, in which tannic acid is utilized successfully as an eco-safe catalyst for synthesis of fused pyrimidines.
Novel heterocyclic dihydropyrimidine chromenopyrimidine-2,5-diones and thioxochromenopyrimidin-5-ones were synthesised by a three-component reaction between 4-hydroxycoumarin, urea or thiourea, and aromatic aldehydes in H2O under reflux in the presence of sodium dodecyl sulfate (20 mol%) and two drops of acetic acid. The products were obtained in good yields and their structures of all the synthesised compounds were established by spectroscopic methods..