ASYMMETRIC-SYNTHESIS OF ALL STEREOISOMERS OF DEMETHYLSORGOLACTONE - DEPENDENCE OF THE STIMULATORY ACTIVITY OF STRIGA-HERMONTHICA AND OROBANCHE-CRENATA SEED-GERMINATION ON THE ABSOLUTE-CONFIGURATION

Strigol and sorgolactone belong to the class of ''strigolactones'', wh ich are highly potent germination stimulants of seeds of the parasitic weeds Striga and Orobanche. The aim of the present work was to synthe size all four stereoisomers of demethylsorgolactone (6), which lacks t he methyl group in the A-ring of naturally occurring sorgolactone, and to evaluate their activities in the stimulation of germination of Str iga hermonthica and Orobanche crenata seeds. Two diastereomers of deme thylsorgolactone (6) were prepared and resolved in the corresponding e nantiomers. Bioassays revealed that the germination stimulatory activi ty Of ii is comparable to that of strigol and that there exist signifi cant differences in activity among the individual stereoisomers.