莲子草假隔链格孢毒素Vulculic Acid的合成

Synthesis of Vulculic Acid from Nimbya alternantherae

Vulculic acid是从莲子草假隔链格孢(Nimbya alternantherae)的代谢产物中分离得到的一种真菌毒素,它对空心莲子草(Alternanthera philoxeroides)等多种杂草有致病活性,是一种潜在的除草活性物质.本文报道了Vulculic acid的化学合成.从可商业购买的3,4,5-三甲氧基苯乙酸出发,经甲酯化、傅克乙酰化、脱三甲基化、选择性上单甲基化以及水解等5步反应合成了目标产物,总产率为21%.生物活性测试结果表明,合成的Vulculic acid对空心莲子草有致病活性,所致症状与天然Vulculic acid一致.

Vulculic acid is a kind of phytotoxin separated from the metabolite of Nimbya alternantherae,which is a leaf spot fungus isolated from alligatorweed.This phytotoxin can result in plant withered and is a potential herbicide to alligatorweed.The synthesis of vulculic acid using the commercially available 3,4,5-trimethoxyphenylacetic acid as the starting material was described.The whole route involved five steps in 21% overall yield with methyl esterification,followed by Friedel-Crafts acylation,demethylation,selective methylation and hydrolysis reaction.This synthesis takes advantage of a selective methylation reaction using borax as the chelating agent.Synthesized Vulculic acid was dissolved in distilled water to detect its effect on alligatorweed leaf through the method of leaf-puncture-soak.The results show that synthetic Vulculic acid could cause leaf spot,same as the symptom by the native Vulculic acid,at the level of 50 μg/mL after treating for 24 h.These results suggest that synthesized Vulculic acid should be good prospect for the application in the control of alligatorweed.