Phthalimide-derived strigolactone mimics as germinating agents for seeds of parasitic weeds

Abstract

Broomrapes attack important crops, cause severe yield losses and are difficult to eliminate because their seed bank is virtually indestructible. In the absence of a host, the induction of seed germination leads to inevitable death due to nutrient starvation. Synthetic analogues ofgermination-inducing factorsmay constitute a cheap and feasible strategy to control the seed bank. These compounds should be easy and cheap to synthesise, as this will allow their mass production. The aim of this work is to obtain new synthethic germinating agents.

Nineteen N-substituted phthalimides containing a butenolide ring and different substituents in the aromatic ringwere synthesised. The synthesis started with commercially available phthalimides. The complete collection was assayed against the parasitic weeds Orobanche minor, O. cumana, Phelipanche ramosa and P. aegyptiaca, with the synthetic strigolactone analogue GR24 used as a positive control. These compounds offered low EC50 values: O. cumana 38.3 𝝁M, O. minor 3.77 𝝁M, P. aegyptiaca 1.35 𝝁Mand P. ramosa 1.49 𝝁M.

The synthesiswas carried out in a fewsteps and provided the target compounds in good yields. The compounds tested showed great selectivity, and low EC50 values were obtained for structures that were simpler than GR24.