Acylalanines

RNA Synthesis. The phenylamides comprise a diverse group of systemic compounds of which the acylalanines are the most successful (Figure 4.11). The acylalanine fungicides are systemic, mainly via the... 

The acylalanines are characterised by metalaxyl, the most studied member of the group. Metalaxyl exists as two enantiomers, metalaxyl M being the most active. Metalaxyl is known to interact with the RNA polymerase-I-template complex,8 inhibiting the incorporation of ribonucleotide triphosphates into ribosomal RNA. 

Acetamide, triazine, carbamate, pyre-throid, urea derivatives, triazinone, acylalanine Phenolic transformation products /V-Methyl carbamate, triazine, phenylurea... 

Within the past ten years, the market introduction of several new types of fungicides has significantly improved the prospects of controlling the Oomycetes. They belong to five different chemical classes the carbamates, the isoxazoles, the cyanoacetamide oximes, the etheyl phosphonates, and the acylalanines and related compounds. The chemical structures of those chemicals that have reached the commercial level are shown in Figures 3-5 (29, revised). Trade names, formulations and first reports are summarized in Table II (29, revised). The biological characteristics of these new fungicides and their impact on disease control have been reviewed by several authors (10, 16, 27, 28, 29, 33). 

The new compounds are used at substantially lower rates than the conventional protectant fungicides (Table V), thus reducing the amount of chemicals brought into the environment. In addition, the acylalanines can be used as seed dressings at extremely low rates. 

Metalaxyl and most of its active analogues are chiral molecules. Chirality is caused by the asymmetric carbon atom in the alkyl side chain of the alanine moiety. The two optically pure enantiomers S (+) and R (-) differ widely in their biological activity both in vitro and in vivo. In all experiments, the R (-) enantiomer was more active than its antipode S (+) (22, 24, 30). The main characteristics of metalaxyl have been discussed in detail by several authors (J, 21, 28, 29, 32> 38). Of particular value is the rapid uptake of metalaxyl by the plant tissue, especially under the wet conditions that favor foliar Oomycete diseases. Acylalanines are easily translocated in the vascular system of the plant after foliar, stem or root treatment (35, 47). The predominant route of transport is the transpiration stream, thus apoplastic (12, 35). Symplastic transport occurs but is much less evident (35, 47). In potatoes treated by foliar sprays of metalaxyl concentrations (0.02-0.04 ppm), Bruin et al. (SO were able to demonstrate protection of harvested tubers from late blight. 

With reference to the acylalanines, it can be stated that whenever they were introduced in mixtures, according to the recommended use concept, no cases of resistance leading to economic losses occurred. This use concept recommends a limited number of applications at the time of serious damage potential combined with field monitoring programs (39). In the interest of the user, the manufac-... 

Bruin, G.C.A. 1980. Resistance in Peronosporales to acylalanine-type fungicides. Ph.D. thesis Univ. Guelph, Ontario, Canada, 110... 

Schwinn, F.J., Staub, T., and Urech, P.A. 1977. Die BekHmpfung Falscher Mehltaukrankheiten mit einem Wirkstoff aus der Gruppe der Acylalanine. Mitt. Biol. Bundesantalt Land Forstwirtsch. Berlin-Dahlem 178. 145-146. 

Staub, T., Dahmen, H. and Schwinn, F.J. 1978. Biological characterization of uptake and translocation of fungicidal acylalanines in grape and tomato plants. Z. Pflanzenkr. Pflan-zenschutz 85, 162-168. 

Staub, T., Dahmen, H., Urech, P., and Schwinn, F. 1979. Failure to select for in vivo resistance in Phytophthora infestans to acylalanine fungicides. Plant Dis. Rep. 63, 385-389. 

The new fungicides being developed for use on grapes in the US fall into three categories ergosterol biosynthesis inhibitors acylalanines, and dicarboximides. 

Three acylalanine compounds, metalaxyl (Ridomil), cyprofuram (Vini-cur) and benalaxyl (Galben), have been tested extensively for control of grape downy mildew in New York. None of these compounds are currently registered in the US. They are narrow spectrum, but highly effective compared to standard protectants such as captan, folpet or mancozeb. They have local systemic activity and possess protectant and antisporulant, as well as after-infection activity. Similar to the EBI compounds, the after-infection capabilities and their activity over extended intervals (14-21 days) make the acylalanines desirable tools for IPM programs. 

An after-infection approach to controlling downy mildew could be developed, providing growers monitor downy mildew infection periods using the same instrumentation discussed under black rot. Acylalanine tank-mixed with folpet or mancozeb would be applied after a... 

Metalaxyl or methyl-N-(methoxyacyl)-N-(2,6-xylyl)-DL-alaninate Acylalanine Inhibits protein synthesis in fungi, systemic with protective action Control of air- and soil-bome diseases on crops 11-29... 

The hydrolysis of L-A -acylalanine methyl esters catalysed by a-chymotrypsin have the following values of Take data from Table 10. 

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