Abstract
A novel pro-insecticide, 29-fluorostigmasterol, is proposed to cause mortality due to release of fluoroacetate during side chain dealkylation. The 29-3H-labeled substrate was fed to third instar tobacco hornworms (Manduca sexta) and erythro-2-fluoro-[2-3H] citrate was isolated in 0.012% yield by ion-exchange, silica gel, and reverse-phase chromatography of the tricarboxylic acid, trimethyl ester, and trimethyl ester benzoate, respectively. The less toxic 29-fluoro-[29-3H]sitosterol did not provide sufficient labeled fluorocitrate to allow isolation, while a more toxic 16-3H-labeled 16-fluorofatty acid gave nearly 1% conversion to labeled fluorocitrate. This is the first direct chemical evidence for the fate of the two carbons removed during phytosterol dealkylation in an insect. It is also the first use of labeled fluoroacetate precursors to identify labeled 2-fluorocitrate as an in vivo metabolite of these precursors.
Highlights
General-Unless otherwise noted,materials were obtained from commercial suppliers and used without further purification
IR spectra were determined with a Perkin-Elmer Model 727 instruevidence for the fateof the two carbons removed dur- ment and are reported in wave numbers. 80 MHz ‘H-NMR
We reported a markedly higher toxicity of 29
Summary
General-Unless otherwise noted,materials were obtained from commercial suppliers and used without further purification. The crude product was flash chromatographed (5 g ofSiO,, 22% EtOAc/hexane) to give 86 mg (74%) of [29-3H]1(specific activity, 540 mCi/mmol); 3H-NMR ('H-decoupled) showed a pair of singlet resonances ina 1:l ratio, 63.84 and 3.80, corresponding to thediastereotopic carbinyl tritons atC-29. 29-Fl1ufuoroorromocsiterarote.h in Insects trifluoro-2-chloroethyl)-N,N-diethylamineT.he reaction was stirred contained trimethyl fluorocitrate along with the trimethyl esters of at 0-20 "C for 2 h, thesolvents were removed in uacuo, and 1ml citrate and isocitrate as determined by capillary gas chromatography of 2-propanol in 2 ml of 5% ethylacetate/hexane was added and (Durabond DB-5,0.25 mm X 30 m, 130 "C). The covered at each purification step for 29-fluor0-[29-~H]sitostero(l2), hexane layer was applied to flash silica minicolumn and 14.5 mg (3.6 29-fluor0-[29-~H]stigmastero(4l), and 16-fluor0-[16-~H]hexadecenmCi) of the tritiated fluoroacid 6 (specific activity, 72 mCi/mmol) oic acid (6). After 8-h incubationat 26 "C, insects were frozen and stored at -17 "C until homogenization
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