Fungicides structure determination

Triazoles are similar to triazines in that they also contain three nitrogen atoms in their ring structures, though they have only two carbon atoms in the ring structure. Amitrole and triadimefon are commonly used triazoles. Different groups of atoms that branch off the central ring structure determine the activity of the compound. The triazole compounds are systemic fungicides that inhibit the s)mthesis of a form of vitamin D. Most triazole compounds are stable in water. 

Figure 5,39 Structures of various fungicides used in the control of post-harvest decay in citrus fruits. Reprinted from J. Chrormtogr., A, 912, Fernandez, M., Rodriguez, R., Pico, Y. and Manes, J., Liquid chromatographic-mass spectrometric determination of post-harvest fungicides in citrus fruits , 301-310, Copyright (2001), with permission from Elsevier Science.

The elucidation of the primary site and biochemical mode of action of inhibitors is often difficult and not necessarily associated with the mechanism of resistance in field isolates. Nevertheless, information on the mechanism of resistance can provide evidence to determine the site of action. Therefore, the classification of fungicides is based on crossresistance reactions rather than chemical similarities of structures or proposed modes of action (Table 1). Based on available information in the literature, three categories of inhibitor classes can be made Classes with known mode of action and known mechanism of resistance, classes with proposed mode of action and unknown mode of resistance but wide-spread field resistance, and classes in which resistance is claimed to occur in the field but both mode of action and resistance are not known. 

Other copper compounds showing marked fungicidal activity, but whose precise structures do not appear to have been determined, are summarized in Table 3. Some reports of copper fungicides where even less is known about their coordination chemistry are available. Copper complexes... 

The antibiotic prumycin, a metabolic of Streptomyces strain No. F-1028, is also a potential fungicide, its main range of action involving Botrytis, Sclerotinia and Sphaerotheca spp. It is not toxic to mammals (Hata et al., 1971). The structure of prumycin has been determined by Omura et al. (1972) to be a 2,5-diamino-2,5-dideoxypentose-5D-alanyl derivative (20). 

The activity of a fungicide and its selectivity under real-life conditions in a complex system of the fungal pathogen, the plant, the environment, and time is determined by a multitude of quite different influencing factors [58]. In the optimization process of a lead structure it is useful to separate such influencing factors... 

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