Abiotic stress adversely affects crop production in various parts of the world, decreasing average yields for most of the crops significantly. Among various abiotic stresses affecting agricultural production, drought stress is considered to be the main source of crop losses. Several strategies have been investigated for reducing the impact of drought on crop yield, such as exploiting beneficial effects of crop protection agents, developing drought tolerant crops through transgenic approaches or breeding, but also exploring novel chemical entities inspired by naturally occurring plant hormones. Analogues of plant hormone abscisic acid (ABA) bearing yet unexplored head group and side chain motifs have been prepared within this study based on a combination of structure-based design, in vivo hits and agrochemical experience. It could thus be explored how modifying key parts of ABA influenced receptor affinity and in vivo efficacy against drought stress. In line with X-ray crystallography studies and molecular modeling novel ABA-derivatives with small alkyl, cycloalkyl or haloalkyl substituents in its terpenoid side chain showed strong effects in vitro and in vivo against drought stress in selected crops. Furthermore, cyano-cycloalkyl groups proved to be suitable re-placements of the cyclohexanone moiety leading to ABA analogues with strong activity in vivo.The versatile synthesis of these novel ABA analogues proceeded via Stille or Sonogashira couplings as the key steps enabling us to carry out in-depth SAR studies. In summary, combining novel cyano-cycloalkyl headgroups with novel substituents in the terpenoid side chain afforded the most promising effects against drought stress in crops, particularly canola and wheat.

Quantum of solace for plants: Exploring unprecedented variations of plant hormone Abscisic Acid to identify new lead structures against drought stress in crops

256th National Meeting (2018)

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