A series of 2′(2′,6′)-(di)halogeno-isoxazolopodophyllic acids-based esters, and oxime sulfonates of 2′(2′,6′)-(di)halogenopodophyllones were prepared by structural modifications of podophyllotoxin as insecticidal agents against Mythimna separata Walker. It was found that when 2′(2′,6′)-(di)halogenopodophyllones or 2′(2′,6′)-(di)chloropicropodophyllones reacted with hydroxylamine hydrochloride, the desired products were related with the configuration of their lactones. Three key single-crystal structures of Ie, IIe and IIIb were determined by X-ray diffraction. Especially compounds IIc and Vc showed the highest insecticidal activity. Moreover, some interesting results of structure-insecticidal activity relationships of tested compounds were also observed.

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Significance: Described here is a gold-catalyzed synthesis of 5,6-dihydro-8H-indolizin-7-ones from tethered enynyl b-lactams. The now well recognized selective C-C triple bond activation by the gold catalyst is followed by a 5-exo-dig cyclization and heterolytic fragmentation of the amide functionality to form a highly nucleophilic acyl cation. This species is proposed, without evidence, to undergo cyclization to the enamine to give the indolizinone core. Application of the synthetic methodology to the construction of the naturally occurring indolizidine 167B is described.Comment: The indolizidine and indolizine framework represent a fundamental and important class of heterocycles, which, in view of their use as antituberculosis agents, histamine H 3 receptor antagonists, and microtubule inhibitors, are attractive synthetic targets (). The starting enynyl b-lactams are readily constructed in a simple four step sequence. The substrate scope is moderately studied. However, most of the b-lactams and obtained indolizinone products were prone to decomposition over time. Gold-catalyzed reactions continue to be at the forefront of new synthetic method development (see Reviews below).