New juvenile hormone analogues and their action on Tenebrio molitor pupae

6-[1-(2-phenoxyethoxy)ethoxy]-1,3-benzoxathiole (I) and three new derivatives, differing from it by the introduction of a iodine atom in the positions 2-, 3-, or 4- of the phenyl ring, were synthesised and applied to five groups of ten 0-24 h old Tenebrio molitor pupae, to evaluate their juvenilizing action. These compounds were topically applied at doses of 100, 10, or 1 mu g/pupa in 1 mu l of acetone. The results of these tests were compared with those obtained with the parent compound and with the derivatives of (I) having either a fluorine or a chlorine atom substituted in the same positions. The maximum juvenilizing action of the above mentioned compounds was reached with the fluorine atom in position 4- at the dose of 100 mu g/pupa. At this dose, this compound was significantly more active than either (I) or its 4-chloroderivative.