Bioisosterism between Sulfonyl Group and Phosphoryl Group-The Synthesis of New ALS Inhibitors N-(Arylamino Hydroxyl Phosphoryl)-N'-(4,6-Dimethoxypyrimidine-2-yl)ureas

In view of the isosterism of sulfonyl group (-SO2-) and phosphoryl group [-P(O)(OR)-,R=H, CH3, C2H5, etc], a new type of ureas, that is, N-phosphoryl-N'-(4,6-dimethoxypyrimidin-2yl) ureas 2 were synthesized and shown to be a new class of acetolactate synthase (ALS) inhibitors.

Target Site-Based Resistance to ALS Inhibitors, Glyphosate, and PPO Inhibitors in an <i>Amaranthus palmeri</i>Accession from Mississippi

Extensive acceptance of glyphosate-resistant (GR) row crops coupled with the simultaneous increase in glyphosate usage has sped the evolution of glyphosate resistance in economically important weeds. GR Amaranthus palmeri populations are widespread across the state with some exhibiting multiple resistance to acetolactate synthase (ALS) inhibiting herbicides such as pyrithiobac. A GR and ALS inhibitor-resistant accession was also resistant to the protoporphyrinogen oxidase (PPO) inhibiting herbicide fomesafen. The PPO inhibitor resistance profile and multiple herbicide resistance mechanisms in this accession were investigated. In addition to fomesafen, resistance to postemergence applications of acifluorfen, lactofen, carfentrazone, and sulfentrazone was confirmed. There was no resistance to preemergence application of fomesafen, flumioxazin, or oxyfluorfen. Molecular analysis of the ALS gene indicated the presence of point mutations leading to single nucleotide substitutions at codons 197, 377, 574, and 653, resulting in proline-to-serine, arginine-to-glutamine, tryptophan-to-leucine, and serine-to-asparagine replacements, respectively. The resistant accession contained up to 87-fold more copies of the EPSPS gene compared to a susceptible accession. A mutation leading to a deletion of glycine at codon 210 (ΔG210) of PPO2 gene was also detected. These results indicate that the mechanism of resistance in the Palmer amaranth accession is target-site based, i.e., altered target site for ALS and PPO inhibitor resistance and gene amplification for glyphosate resistance.

Bioisostere of Sulfonyl Moiety-The Synthesis of New ALS Inhibitors N-(Asymmetry Disubstituted Phosphoryl)-N'-(4,6-dimethoxypyrimidin-2-yl) Ureas

In view of the isosterism of the sulfonyl (-SO2-) and phosphoryl groups [-P(O)(OR)-,R=H, CH3, C2H5, etc], two new types of ureas, N-(N-aryl-O-alkyl phosphoryl)-N'-(4, 6-dimethoxypyrinddin-2-yl) ureas 2 and N-(N-aryl-N-alkyl phosphoryl)-N'-(4, 6-dimethoxy pyrimidin-2-yl)ureas 3, were synthesized by treating N- (arylandnochlorophosphoryl ) - N'- (4, 6-dimethoxypyriAndinyl-2-) ureas 4 with alcohols or amines. Compounds 4 were obtained by reactingdichlorophosphoryl isocyanate with 4,6 - di meth oxy- 2-aminopyrimidine, and then with aromaticamines. The enzyme tests (in vitro) indicated that compounds 2 and 3 were two novel classes ofacetolactate synthase (ALS) inhibitors, which showed that the phosphoryl group, [-P(O)(OR)-], or[-P(O)(NHR)-], was a good bioisostere of the sulfonyl group (-SO2-) in sulfonylurea.

Efficiency of Chalcone Compounds Inhibitors for Acid Corrosion of Al and Al-3.5Mg Alloy

Corrosion inhibition of Al and Al-3.5Mg alloy by organic compounds, namely chalcones in hydrochloric acid solutions has been investigated by rapid polarization technique and weight loss method. Polarization measurements show that, the inhibitors act cathodically both in case of Al and Al-3.5Mg alloy. It was found from the weight loss measurements that, the inhibition efficiency depends on the substituent in the chalcone compound. The relative inhibitive efficiency of these compounds has been explained on the basis of structure dependent electron donor properties of the inhibitors and the metal inhibitor interaction on the surface. The inhibition efficiency ranges from 16 to 64% for Al and from 30% to 91% for Al-3.5Mg alloy

Tribenuron-Methyl Resistant Flixweed(Descurainia sophia)

Flixweed seeds were collected from suspected winter wheat fields and remote hillside in Shaanxi Province, China, their sensitivities to tribenuron-methyl were evaluated in the greenhouse. Results revealed that biotype S was susceptible to tribenuron, and its GRs0 was 0.23 g a.i. ha^-1, whereas biotypes R1, R2, R3, and R4 were resistant to the tribenuron, and their GR50 were 161.99, 79.70, 439.80, and 312.30, respectively. Biotypes R1 and R2 showed moderate resistance with resistant indices （RI） of 615.23 and 302.7, respectively. Whereas biotypes R3 and R4 showed high resistance to the herbicide with RI values as high as 1 670.34 and 1 186.10, respectively.

Tribenuron-Methyl Resistant Shepherd's Purse (Capsella bursa-pastoris (L.) Medik.) in Hebei Province of China

Shepherd＇s purse seeds were collected from winter wheat fields and road sides in Hebei Province,China.Their sensitivities to tribenuron-methyl were evaluated in a whole plant dose response assay in the greenhouse.Results revealed that HB-1,HB-2,HB-3,HB-4,HB-6,HB-7,HB-17,HB-18,HB-19,HB-20,HB-21,and HB-22 populations were susceptible to tribenuron-methyl characterised by very low GR50 values of about 0.10 g a.i.ha-1.On the other hand,populations HB-15 and HB-16 had moderate resistance to tribenuron-methyl with resistance indices （RI） ranging from 10-100 folds,whilst populations HB-5,HB-8,HB-9,HB-10,HB-11,HB-12,HB-13,and HB-14 expressed high level of resistance to tribenuron-methyl with resistance indices over 100.The proportion of moderate resistance level was about 9.09%,and that of high resistance was about 36.36%.

Efficacy of Trifluralin Compared to Ethalfluralin Applied Alone and Co-Applied with Halosulfuron for Weed Management in White Bean

There are a limited number of herbicides registered for weed management in white bean production in Ontario, Canada. Five field experiments were completed in Ontario from 2016 to 2018 to compare the efficacy of trifluralin and ethalfluralin applied alone and in combination with halosulfuron, applied preplant incorporated (PPI), for weed control efficacy and white bean tolerance and seed yield. At 2 and 4 WAE, there was no white bean injury from the herbicide treatments evaluated. Trifluralin applied PPI provided up to 32%, 99%, 13%, 99%, 27%, 99% and 99% control of velvetleaf, redroot pigweed, common ragweed, common lambsquarters, wild mustard, barnyardgrass and green foxtail, respectively. Trifluralin and ethalfluralin provide similar control of velvetleaf, redroot pigweed, barnyardgrass and green foxtail control, however, ethalfluralin is slightly more efficacious on common ragweed, common lambsquarters and wild mustard. Halosulfuron (35 g∙ai∙ha−1), applied PPI, provided as much as 76%, 98%, 96%, 96%, 100%, 19% and 23% control of velvetleaf, redroot pigweed, common ragweed, common lambsquarters, wild mustard, barnyardgrass and green foxtail, respectively. Trifluralin (600 or 1155 g∙ai∙ha−1) + halosulfuron (35 g∙ai∙ha−1), applied PPI, provided up to 88%, 100%, 98%, 100%, 100%, 99% and 98% control of velvetleaf, redroot pigweed, common ragweed, common lambsquarters, wild mustard, barnyardgrass and green foxtail, respectively. Ethalfluralin (810 or 1080 ai∙ha−1) + halosulfuron (35 g∙ai∙ha−1) provided similar control. Weed interference decreased white bean seed yield 44% - 45% with trifluralin, 30% - 41% with ethalfluralin and 34% with halosulfuron. However, decreased weed interference with trifluralin and ethalfluralin applied in combination with halosulfuron resulted white bean seed yield that was similar to the weed-free control. Trifluralin or ethalfluralin co-applied with halosulfuron can be safely used in white bean production for the control of common annual grass and broadleaf weeds in Ontario.

Design,synthesis and biological activity of novel herbicides targeted ALS(Ⅻ)--Quantitative structure-activity relationships of herbicidal l,2,4-triazolo[l,5-a]pyrimidine-2-sulfonanilides

The herbicidal activities of a series of 1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonanilides containing various substituents on the benzene ring were quantitatively analyzed with physicochemi-cal parameters by using Hansch-Fujita method.Variations in the activity were parabolically related to electronic parameters with the optimum pKavalue being about 6.93.The hydrophobic factor in addition to the electronic property seemed to have important effect on the activity.

Design, synthesis and bioactivity of novel herbicides targeted ALS (Ⅶ): Quantitative structure-activity relationships of herbicidal sulfonylureas

The quantitative relationship between the structures of 20 sulfonylureas and their herbicidal activities against rape was analyzed using physicochemical parameters and regression analysis. The results showed that the electronic properties of the molecules are the dominant factor to the activity and there is apparently an optimum electronic property (∑σ or pKa) for the molecules to fit the receptor. Combined with the previous QSAR results for herbicidal triazolopyrimidine-2-sulfonamides, we can conclude that the structure-activity relationships of these two sets of compounds are identical, which suggested that these two sets of compounds acted on the same target site.