Synthesis of jasmonates and derivatives to study plant signaling : activation translocation and shutdown mechanisms Endogenous jasmonates (plant hormones) and synthetic derivatives were synthetized to study different aspects of plant signaling. In a first study new evidence of the close relationship between the Ca2+ and JA signaling pathways is provided. It is reported that the antibiotic neomycin selectively blocks the Ca2+ elevation induced by oral secretions of Spodoptera littoralis larvae and consequently inhibit the accumulation of the active jasmonate JA Ile in the leaves of Arabidopsis thaliana plants. A second study uses a fluorinated mimic of the JA precursor OPC 8:0 as a molecular probe to study its metabolism in planta. The fluorinated compound and derived metabolites can be detected by UHPLC MS MS easily. The fluorinated OPC 8:0 can be translocated from damaged to undamaged systemic leaves. This result suggests that OPC 8:0 ─ in addition to JA and JA Ile ─ may also contribute to propagate the mobile signal which induces systemic defense responses in plants. The third case of study reports on the possibility of manipulating the JA signalling pathway by modifying the endogenous ligand JA Ile. Based on the crystal structure of the JA Ile receptor two JA Ile derived macrolactones were prepared. Both synthetic lactones induce nicotine accumulation to a similar extent as MeJA does in Nicotiana attenuata leaves. Finally the JA Ile inactivation mechanism upon ω hydroxylation is investigated by using a chemical approach. It was found that impaired activity of 12 OH JA Ile is likely due to steric hindrance caused by the ω–OH. Furthermore a convenient synthesis of 12 modified jasmonates is described. The methods discussed in this Dissertation should complement established molecular biology techniques to study plant physiology. New knowledge of the molecular mechanism of JA Ile signalling ─ from early events like Ca2+ induced JA Ile burst until late events like the switch off of the jasmonate signal ─ is presented.