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

Abstract

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.

The Use of Arabidopsis to Study Interactions between Parasitic Angiosperms and Their Plant Hosts

“…The most common class of germination stimulants are sesquiterpene lactones, collectively referred to as strigolactones (Wigchert and Zwanenburg, 1999) (Figure 2). Strigolactones stimulate germination at low concentrations (10 -8 to 10 -12 M) and structural studies of natural and synthetic analogs revealed that bioactivity resides in the C and D rings with their absolute configuration being critical (Thuring et al, 1997). Together these results suggest that Striga perceives these molecules through a receptor-mediated process (Mangus and Zwanenburg, 1992).…”

The Biosynthetic Origin of Germination Stimulants for Orobanche Ramosa (L.) in Tobacco and Arabidopsis

“…Although the GS and their analogs were synthesized by organic synthesis (23,24), their biosynthetic origin remained unknown. The knowledge about the biochemistry and genes responsible for GS production in host plants may answer many questions about mechanisms of co-evolution of parasites and their hosts and on the other hand will lead to development of new practical measures for control of crops-harming parasitic species (14).…”

IAA production during germination of Orobanche spp. seeds

“…All of these compounds isolated from different hosts of Striga and Orobanche are generally known as strigolactones (Galindo et al, 2002). In addition to this more or less narrow host specificity, the parasite's seeds are able to respond to synthetic germination stimulants, strigolactone analogues, termed GR compounds (Thuring et al, 1997;Sugimoto et al, …”