Herbicide groups, structure-activity

None of these had pronounced herbicidal activity but rather PGR activity. Compound % for example, has been shown to be an auxin transport inhibitor, a property probably shared by the other members of this class also. A structure activity analysis for this group of compounds has been reported by Katekar ( ) ... 

Structure-activity studies have shown the crucial role of the trifluoromethyl group in optimum biological activity of bleaching herbicides [38], Isoxaflutole (Balance , Merlin ) is a root or foliar uptake systemic herbicide with broad-spectrum control in corn and sugarcane of both grass and broadleaf weeds [39], Isoxaflutole is rapidly converted in plants and in soil to the diketonitrile form, which is the biologically active species (Fig. 7) [40],... 

Another example of a trifluoromethyl heteroaryl-containing herbicide is di-thiopyr (Dimension ) [72], Structure-activity studies have demonstrated that a fluorinated alkyl group is required for optimum activity at the 2 and/or 6 positions of the pyridine ring [73], Thiazopyr (Mandate , Visor ), a herbicide related to dithiopyr, was introduced by Monsanto in 1992 and later sold to Rohm and Haas. It is used for the pre-emergence control of annual grass and a few broadleaf weeds in tree fruit, vines, sugar cane, and other crops. 

Aryloxyphenoxypropanoates and cyclohexanediones are two classes of herbicides that control many monocotyledoneous species. Although these herbicides are structurally very different (Fig. 1), there has been some conjecture that they have a similar mode of action because of their similarity in selectivity and symptomology. This paper describes the experiments that led to the discovery that aryloxyphenoxypropanoate and cyclohexanedione herbicides inhibit acetyl coenzyme A carboxylase (acetyl-coenzyme A bicarbonate ligase [ATP], EC 6.4.1.2) activity in susceptible species (1). In addition, evidence is presented indicating that the inhibition of acetyl coenzyme A carboxylase (ACCase) is well correlated to observed herbicidal activity. Similar, independent findings have recently been reported by two other research groups (2.3). 

The first chapter in the herbicide section is devoted to synthetic efforts related to the herbicide Command, currently being developed by FMC Corporation. Here we see detailed the various synthetic and structure-activity relationships of this important group of compounds. These compounds exert their phytotoxic effect by their bleaching action on a wide variety of economic weeds. An important observation was that soybeans were not affected at normal use rates. These compounds act upon the carotene and chlorophyll biosynthesis of the plant. Here are a group of synthetic pathways that are peculiar to plants and a few microorganisms and are susceptible to chemical attack. 

Diary] and triaryl or naphthyl carbamates exhibit low herbicidal activity. The substitution of the aryl radical for a heterocyclic radical gives heterocyclic alkyl and dialkyl ureas, of which many examples have been prepared in recent years. The herbicidal activity of urea derivatives containing a heterocyclic radical, such as benzthiazole, thiazole, thiadiazole, oxadiazole and pyridine, is favourable if one or two methyl groups are substituted at the N -nitrogen. The carrier of total or selective action in these derivatives is presumably the heterocyclic part of the molecule. More recently several new groups of compounds have become known, mainly in the patent literature, for which the structure-activity on relationships are still to be elucidated. 

Based on the structure activity trends of the pyrimidine sulfonylureas, we wanted to examine analogs with groups that we expect to be more activating as herbicides ... 

In order to obtain more powerful PDHc El inhibitors with effective herbicidal activity, all substituents R, R, R, R, and Yn in structure I were systemically modified. Through structural modification or optimization, more than thirty novel series of structure I including alkylphosphonates, monosalts of alkylphosphonic acids, alkylphosphinates, monosalts of alkylphosphinic acid, cycUc phosphate, and caged bicyclic phosphates were designed and synthesized (Scheme 1.20). Their herbicidal activities were evaluated. Structure-activity relationship was then established and analyzed. Enzyme inhibition, toxicities and usage of representative compounds in this group were also stodied later. 

C21-0017. Shown below is a ball-and-stick model of the active ingredient in Roundup, a commercial herbicide. Draw the Lewis structure of Roundup and describe its functional groups. 

Endothall is a structural analogue of cantharidin (Fig. 20). Its mode of action is apparently inhibition of protein phosphatase(s). A struc-ture/activity relationship study demonstrated that the presence of the oxygen bridge and the location of the two carboxylic groups play important roles in the activity of the molecules. The unusual 7-oxabicyclo[2.2.1]heptane ring of endothal is similar to that of cinmethylin, another natural product-like herbicide for which the mode of action has also eluded scientists for many years. 

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