Dimethoxypyrimidines as novel herbicides. Part 4. Quantitative structure-activity relationships of dimethoxypyrimidinyl(thio)salicylic acids
✍ Scribed by Nezu, Yukio; Wada, Nobuhide; Yoshida, Fumitaka; Miyazawa, Takeshige; Shimizu, Tsutomu; Fujita, Toshio
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 276 KB
- Volume
- 52
- Category
- Article
- ISSN
- 1526-498X
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✦ Synopsis
The activity of a number of O-(4,6-dimethoxypyrimidin-2-yl)salicylic acids and their thio analogs inhibiting acetolactate synthase (ALS) preparation was measured. The e †ects of substituents on the salicylic-benzene ring on the inhibitory activity were analyzed quantitatively with physicochemical substituent parameters. For 6-substituted (thio)salicylic acids, the activity was shown to vary parabolically with the "intramolecularÏ steric parameter
In addition, the (E s ). higher steric dimension of substituents in terms of the STERIMOL width or length parameter lowered the activity. The Ðeld-inductive electron-withdrawing property of the 6-substituents in terms of the SwainÈLuptonÈHansch F was favorable for the activity of salicylic acid series. In 5-substituted salicylic acids, the activity was increased by electron-donating substituents with smaller size. The relationships between ALS inhibitory and herbicidal activities were also analyzed with some weed species. Both pre-and post-emergence activities against barnyard grass, Echinochloa crus-galli, were linearly related to the ALS inhibitory activity after allowing for the hydrophobic factor that may contribute to the transport processes. Those against two broad-leaved weed species, Polygonum convolvulus and Abutilon theophrasti were linearly related to the in-vitro activity with no signiÐcant participation of the hydrophobic factor.
1998 SCI (