Configurational stereoisomer of difethialone, composition and rodenticidal bait comprising same, and process for controlling target rodent pests

Process for controlling target rodent pests, in which there is spread an amount of bait comprising:

• at least one excipient that is edible for target rodent pests;
• and
• the laevorotatory enantiomer of the configurational stereoisomer of difethialone, named hetero-stereoisomer, the formula of which is 3-(4′-bromobiphenyl-4-yl)-1-(4-hydroxythiocoumarin-3-yl)-1,2,3,4-tetrahydronaphthalene, in which carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group have different absolute configurations;
• with the exclusion of a racemic mixture of the laevorotatory and dextrorotatory enantiomers of said hetero-stereoisomer of difethialone.

Chromatographic process for obtaining a laevorotatory enantiomer of a configurational stereoisomer of difethialone, named hetero-stereoisomer, the formula of which is 3-(4′-bromobiphenyl-4-yl)-1-(4-hydroxythiocoumarin-3-yl)-1,2,3,4-tetrahydronaphthalene, in which carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group of said hetero-stereoisomer have different absolute configurations, in which process:

• a high-pressure liquid chromatography column of dimensions 150×2 mm, and comprising a chiral stationary phase constituted of particles of tris(4-methylbenzoate) cellulose, said particles having a mean size of 3 μm and having a mean pore size of 1000 Å, is chosen;
• a mixture formed from acetonitrile (A) and water comprising 0.1% by volume of formic acid (B), with an A/B volume ratio of 80/20 and with a flow rate of the liquid mobile phase in the chromatography column of 0.25 mL/minute, is chosen as liquid mobile phase;
• separation of the configurational stereoisomers of difethialone is performed at room temperature, during which:
• a liquid composition comprising said laevorotatory enantiomer of said hetero-stereoisomer of difethialone is introduced into the top of the chromatography column;
• and then
• the liquid composition is entrained with the mobile phase in the chromatography column under conditions suitable for separating the configurational stereoisomers of difethialone;
• and
• a fraction of the mobile phase comprising said laevorotatory enantiomer of said hetero-stereoisomer of difethialone is collected with a retention time t2 having a value such that t1<t2<t3<t4;
• t1, t3 and t4 representing the retention times of each of the configurational stereoisomers of difethialone different from the laevorotatory enantiomer of said hetero-stereoisomer of difethialone, separately from a dextrorotatory enantiomer of said hetero-stereoisomer of difethialone with a retention time t3 and separately from the laevorotatory and dextrorotatory enantiomers of a configurational stereoisomer of difethialone, named homo-stereoisomer, in which carbons 1 and 3 of the 1,2,3,4-tetrahydronaphthalene group of said homo-stereoisomer have the same absolute configuration, and of retention times t1 and t4;
• and then
• the liquid mobile phase of said fraction is removed so as to obtain said laevorotatory enantiomer of said hetero-stereoisomer of difethialone.