Due to their promising biological properties, different natural products from fungi of the genus Hygrophorus were synthesized and investigated on their antifungal properties against various phytopathogens in the context of this work.Fatty acids with γ-oxocrotonate structure were accessible in a simple synthetic sequence from furan. To optimize the antifungal properties, all structural elements were modified and structure-activity relationships were evaluated. Furthermore, hygrophorones were synthesized in an asymmetric total synthesis. Key steps in this synthesis were a Sharpless dihydroxylation, an aldol reaction and a Dieckmann-type cyclization. The absolute configurations of all stereocenters were completely elucidated by NMR spectroscopy and a single crystal X-ray analysis. In addition, also cyclopentenones, which were structurally closely related to hygrophorones, but synthetically easier accessible, were also synthesized.