Disclosed is a configurational stereoisomer, named enantiomer E1, of flocoumafen, the enantiomer E1 having, by chromatographic analysis of flocoumafen performed under particular conditions, a retention time t1 having a value such that t1<；t2<；t3<；t4； t2, t3 and t4 representing the retention times of the configurational stereoisomers of flocoumafen different from the enantiomer E1, the analysis being performed at a temperature of 23.5° C.
