To search for improved insecticidal compounds based on β-dihydroagarofuran sesquiterpenoids, forty-four β-dihydroagarofuran acetal derivatives were designed and synthesized. Insecticidal activities and structure-activity relationship of these target compounds were evaluated. Some of the newly synthesized β-dihydroagarofuran acetal compounds were found to show higher insecticidal activity against sixth-instar larvae of Mythimna separate. Especially, compounds 2.2.9, 2.2.10, 2.2.11, 2.3.4, 2.3.6, 2.3.7, 2.5.4, 2.5.7 had great insecticidal activities with lower LD50 than that of the positive control celangulin-V (110.13 μg/g). It deserves mentioning that compound 2.2.11 showed the lowest LD50 (60.33 μg/g) among these compounds. Structure-activity relationship results suggested that the substituent groups of 1-, 6- and 9-positions of the target structures could greatly affect the insecticidal activity. Especially, when the substituent groups of 6-position were n-propyl, n-butyl, allyl, propargyl, o-fluorobenzyl, and p-fluorobenzyl, the compounds showed outstanding insecticidal activities.
