Alternariol and monomethylalternariol are natural phytotoxins produced by some fungal strains, such as Nimbya and Alternaria. These substances confer virulence to phytopathogens, yet no information is available concerning their mode of action. Here we show that in the micromolar range alternariol 9-methyl ether is able to inhibit the electron transport chain (IC50 = 29.1 +/- 6.5 mu M) in isolated spinach chloroplasts. Since its effectiveness is limited by poor solubility in water, several alternariol analogues were synthesized using different aromatic aldehydes. The synthesized 6H-benzo[c]cromen-6-ones, 5H-chromene[4,3-b]pyridin-5-one, and 5H-chromene[4,3-c]pyridin-5-one also showed inhibitory properties, and three 6H-benzo[c]cromen-6-ones were more effective (IC50 =12.8-22.8 mu M) than the lead compound. Their addition to the culture medium of a cyanobacterial model strain was found to inhibit algal growth, with a relative effectiveness that was consistent with their activity in vitro. In contrast, the growth of a nonphotosynthetic plant cell culture was poorly affected. These compounds may represent a novel lead for the development of new active principles targeting photosynthesis.
A metal-free one-pot synthesis of benzo[c]chromen-6-ones from 3,4-dichlorocoumarins and butadienes using tandem photo-thermal-photo reactions
of biologically valuable benzo[c]chromen-6-ones is achieved using a tandem photo-thermal-photo reaction sequence starting from 3,4-dichlorocoumarins and a 1,3-butadiene. In this concise one-pot protocol, neither metal catalyst nor peroxide promoter is needed and the products can be purified through simple recrystallization in most cases. The synthesis consists of a reaction sequence of photo-induced
使用从3,4-二氯香豆素和1,3-丁二烯开始的串联光热反应过程,可以有效,简单,通用地合成具有生物学价值的苯并[ c ] chromen-6-one。在这种简洁的一锅法方案中,不需要金属催化剂或过氧化物促进剂,并且在大多数情况下,可以通过简单的重结晶来纯化产物。合成过程包括光诱导的[4 + 2]和[2 + 2]环加成反应的顺序,硅胶促进的HCl消除和电环环丁烯开环,然后进行光诱导的6π电环化。用一系列二氯香豆素和一些典型的丁二烯可以很好地进行反应,从而以70-80%的产率提供相应的环状产物。