RESOLUTION AND BIOLOGICAL-ACTIVITY OF BOTH ENANTIOMERS OF METHAMIDOPHOS AND ACEPHATE

Both enantiomers, optically pure, of methamidophos, O,S-dimethyl phosphoramidothioate (1), and acephate, O,S-dimethyl N-acetylphosphoramidothioate (2), were prepared by optical resolutions via diastereomers with L-proline ethyl ester and by HPLC using a chiral adsorbent, respectively. The (R)P-(+) enantiomers were more potent to houseflies than the optical antipodes and racemates. In contrast the (S)p-(-) enantiomers were more toxic within 12 h after application against German cockroaches, although the 24-h LD50 values were not significantly different among both enantiomers and racemate of 1, as well as 2.