Asymmetric Synthesis of All Stereoisomers of the Strigol Analogue GR24. Dependence of Absolute Configuration on Stimulatory Activity of Striga hermonthica and Orobanche crenata Seed Germination

All four optically pure stereoisomers of the strigol analogue GR24 were prepared via two different routes. In the first approach enantiopure ABC-fragments 4 were used as the chiral source, whereas in the alternative route both antipodes of the latent D-ring 6 were employed. Bioassays revealed significant differences in activity between the four stereoisomers in the stimulation of germination of the parasitic weeds Striga hermonthica and Orobanche crenata. Keywords: Striga; Orobanche; germination, GR24