Pyrimidinylsalicylic Based Herbicides: Modeling and Prediction (original) (raw)

2011, Herbicides and Environment

The necessity of increasing the productivity per cultivation area is a peremptory demand since, on hand, the available surface is limited, even worse it has diminished due to the degradation of the soil; and on the other hand, it is necessary to supply the food demand of a steadily increasing population. To supply this demand of the current world population, about six thousand million, it is required to produce more and more. To do this is necessary to use massively chemicals, known generically as agrochemicals (insecticides, fungicides, acaricides, nematocides and herbicides). The use of these chemicals has allowed for significant reduction of the agriculture plagues and consequently increased the productivity. Among the pesticides, the herbicides deserve special attention since, due to the resistance developed by weeds, new products have to be steadily introduced to market. Plants and many microorganisms are able to synthesize from inorganic precursors all the metabolites needed for their survival. In contrast, animals must obtain many compounds, such as vitamins, essential fatty acids and certain amino acids, from their diet. This is because they lack the full biosynthetic machinery, so there are metabolic pathways and their component enzymes that are not found in animals. The branched-chain amino acids (BCAAs) are synthesized by plants, algae, fungi, bacteria and archae, but no by animals. Therefore, the enzymes involved in the BCAA biosynthetic pathway are potential targets for the development of herbicides, fungicides, and antimicrobial compounds. Pyrimidinylsalicylic acid (PSA) based compounds show potent herbicidal activity. This activity has been identified as a result of the inhibition of acetohydroxyacid synthase, AHAS. Unfortunately, this family of compounds has been poorly characterized from the physical-chemical point of view. This lack of information has prevented the assessment of their impact in the environment. The difficulty to obtain accurate experimental values arise mainly from limitations of analytical techniques, cost, safety and time. For this reason, it is very useful to be able to predict these properties. Such a prediction may be important additionally for the design of novel herbicides since their properties could be predicted prior to synthesis and consequently the design may, in this way, be guided by the results of calculations. Once these properties are known the effect of these chemicals on the environment could be evaluated in advance, reaching in this way the desired compromise