Total synthesis and herbicidal activity of natural rubrolides C, E and F

Rubrolides are natural butyrolactones isolated from the tunicate Ritterella rubra, shows antibacterial, antiviral and plant photosynthesis inhibitory activities. In this study, a facile total synthetic method for preparing the rubrolides from benzaldehyde by a Darzens reaction, aldol reaction and vinylogous aldol condensation in five steps is presented. Three natural rubrolides (E, C and F) were synthesised in the total yields of 25-40%. The bioassay results indicate that rubrolides E, C and F exhibit some herbicidal inhibitory effect against rapeseed, in particular, rubrolide F shows the best herbicidal activities against rapeseed root with the growth inhibitory rate of 72.8%. At greenhouse treatment concentrations of 100 and 500 mg/L, rubrolide F show a positive dose-toxicity correlation towards abutilon plants. Collectively, facile total Synthesis strategy provided the base for further bioactivities study of rubrolides family. Rubrolide F may be act as inhibitor of photosynthesis, and this could be lead structure of new herbicide.