Tetsuo Okauchi

On the origin and metabolic fate of α-ecdysone in insects☆

Abstract Injected or ingested 3 H-α-ecdysone in Bombyx larvae during the last (fifth) larval instar is rapidly distributed throughout the body and is converted to β-ecdysone and three polar metabolites (designated compounds A, B, and C) separated by liquid chromatography. Compound A, which may be an acidic sidechain-cleavage fragment of α-ecdysone containing C-23 and C-24, is excreted into the gut. Compound C can be hydrolyzed to β-ecdysone and may be an ester conjugate with a polar acid. Nothing is known about the structure of compound B. The conversion of α- to β-ecdysone occurs throughout the fifth instar of Bombyx ; the rate of conversion increases, and the rate of further metabolism of the formed β-ecdysone decreases markedly towards the time of pupation. The conversion of α- to β-ecdysone occurs efficiently in isolated abdomens of Calliphora and Bombyx , thus indicating that the ecdysial gland may not be the site of this conversion, and that the observed hormonal effect of α-ecdysone may be due in part to its prior metabolism to β-ecdysone.

Biosynthesis of agr and beta-Ecdysones from Cholesterol outside the Prothoracic Gland in Bombyx mori.

Labeling experiments have established that cholesterol is converted into α-and β-ecdysones in isolated abdomens of silkworm larvae. Since the isolated abdomens do not contain the prothoracic glands, a doubt is cast on the long-standing principle in insect endocrinology that the prothoracic glands are the source of ecdysone secretion.

Synthesis and insecticidal activity of nitroguanidine derivatives

Nitroguanidine derivatives with thiazol-5-ylmethyl moieties were prepared and their insecticidal activities against homopterous pests were tested. New synthetic routes for 2-chloro-5-chloromethylthiazole from 2,3-dichloro-1-propene and for substituted nitroguanidines from S-methyl-N-nitroisothiourea were established. Biological evaluation led to a novel insecticide (E)-1-(2-chlorothiazol-5-ylmethyl)-3-methyl-2-nitroguani dine (TI-435) which has a broad activity spectrum and is under development. ©1999 Society of Chemical Industry