The N'-benzoyl group of N-tert-butyl-N'-benzoyl-3,5-dimethylbenzohydrazide (1) was converted to a series of benzoheterocyclecarbonyl groups in order to investigate the potential usefulness of superimposing a hydrazine insecticide on 20-hydroxyecdysone. A series of analogues with benzodioxole, benzodioxane, benzodioxapine, indole, benzoxazole, benzoxazine or benzothiazole instead of the phenyl group of (1) were synthesized and tested for their insecticidal activity against the common cutworm (Spodoptera litura F). N-tert-Butyl-N'-(3,5-dimethylbenzoyl)-1,3-benzodioxole-5-carbohydrazide and N-tert-butyl-N'-(3,5-dimethylbenzoyl)-2,3-dihydro-1,4-benzodioxine-6-carbohydrazide showed high insecticidal activities, superior to that of (1) and equal to that of the commercial insecticide tebufenozide (RH-5992).

A series of N'-benzoheterocyclecarbonyl-N-tert-butyl-3,5-dimethylbenzohydrazide analogues possessing a variety of substituents on the benzene rings of the benzoheterocyle moieties were synthesized and tested for their insecticidal activity. The introduction of a methyl group at the R1 position of the benzoheterocycle moiety strongly increased the insecticidal activity. Among the analogues synthesized, N'-tert-butyl-N'-(3,5-dimethylbenzoyl)-5-methyl-6-chromanecarbohydrazide showed the highest insecticidal activity (LC50 = 0.89 mg litre(-1)).

Nineteen analogues were synthesized by modifying the tert-butylhydrazine moieties of N'-tert-butyl-N'-(3,5-dimethylbenzoyl)-5-methyl-2,3-dihydro-1,4-benzodioxine-6-carbohydrazide and N'-tert-butyl-N'-(3,5-dimethylbenzoyl)-5-methylchromane-6-carbohydrazide (chromafenozide), and the synthesized analogues were evaluated for their insecticidal activity against Spodoptera litura F. While all of the synthesized analogues had insecticidal activity inferior to those of the lead compounds, several of the analogues nonetheless showed high insecticidal activity. Chromafenozide has shown very high selectivity toward lepidopteran species.

Starting from milbemycin D (1), milbemycin A4 (2) and milbemycin A3 (3), a series of 5-keto-5-oxime derivatives were synthesized by selective oximation at the a,/?-conjugated carbonyl function of the 5-ketomilbemycins (4-6). The activities of the synthesized compoundswere studied in dogs naturally infested with microfilariae of Dirofilaria immitis. The 5-keto-5-oximes of milbemycin D (7), A4 (8) and A3 (9) had quite high efficacy to control the microfilariae and more potency than their parents, while the 5-O-acyl oximes (ll-15) also exhibited high activity. The synthesis of the 5-keto-5-oxime derivatives is shown in Scheme 1. The 5-keto intermediates ofmilbemycin A3 (6) and A4 (5) were also isolated from a culture broth of Streptomyces hygroscopicus, and were named 2615 milbemycin J and K, respectively

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