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A new series of substituted 2-anilino-3-methylbutyrates has been prepared; bioassay data for these compounds on Heliothis virescens, Musca domestica, Aphis fabae and Tetranychus urticae are presented and discussed. Some unexpected relationships were observed between the nature of the substituents and the biological activity. Increases in foliar stability were noted with certain substitution patterns. Both a-cyano-3phenoxybenzyl 3-methyl-2-( a, a, a,2-tetrafluoro-p-toluidino)butyrate and the corresponding 2-(2-chloro-a, a, a-trifluoro-p-toluidino)-3-methylbutyrate showed good stability in air and light, and exhibited biological activities of a similar nature and potency to those of previously known synthetic pyrethroids. Esters of the (R)-2anilino-3-methylbutyric acids are far more active than those prepared from the (S)enantiomers. The (R)-configuration at C-2 in these acids is sterically equivalent to the active absolute configuration at the chiral carbon a to the carboxylate group in both the permethrin and the fenvalerate types of pyrethroids. A new class of insecticidal 2-(isoindolin-2-yl)alkanoates is also reported. In this series the most biologically active analogue was a-cyano-3-phenoxybenzyl 3-methyl-2-(4,5,6,7-tetrafluoroisoindolin-2-yl)butyrate. These esters were considerably less stable than the anilino analogues on exposure to air and light. IntroductionRecent progress in the area of synthetic pyrethroidsl-4 includes the discovery of resmethrin (I) and bioresmethrin,5 the much more photostable compound permethrin (I1),6 the extremely potent analogue NRDC 161 (111),7 and the important analogue fenvalerate (lVd).s-lo The new compounds IT, 111, and IVd possess outstanding potency against a wide range of insect pests, adequate field stability and relatively low mammalian toxicity. Described here are the preparation and structurebiological activity relationships of a number of 2-anilino-3-methylbutyrates and 2-(isoindolin-2-yl)-3-methylbutyrates which show high insecticidal activities similar to those of the conventional pyrethroids containing a cyclopropane ring. ExperimentalOptical rotations were determined on a Perkin-Elmer Model 141 polarimeter. Preparative thinlayer chromatography (t.1.c.) was carried out on 1 rn x 20 cm plates coated with 1.3 mm of Merck a Presented at a symposium Recent advances in the chemistry of the pyrethroids held at St. 224 2-Anilino-3-methylbutyrates and 2-(isoindolin-2-yl)-3-methylbutyrates 225 (Darmstadt) silica gel PF254. Nuclear magnetic resonance (n.m.r.) spectra were determined on a Varian T-60 spectrometer. Mass spectra were measured on a Hewlett-Packard Model 5985 g.1.c.-m.s data system. Analyses by gas-liquid chromatography (g.1.c.) were performed on Model 402 Hewlett-Packard instruments equipped with flame-ionisation detectors. Infrared spectra were measured on Unicam SP 200 G or Perkin-Elmer model 281 spectrophotometers. All new compounds were characterised by their n.m.r., infrared, and mass spectra. CH-CH-COOR' ' I CH3 Br or CH3, CH-C-COOR' ' II 0 CH3 (R' = H, N...

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