Toxophoric structural element

Microbiddes with an activated N-S bond as toxophoric structural element... 

Mierobieides disposing of sueh a toxophoric structural element - as already mentioned, acrolein and a-bromo-einnamaldehyde do that - may add to nucleophilic cell components (Figure 8.) and release their antimicrobial effect in this way. However, sueh substances are only suitable for practical applications, e.g. as non-persistent slimieides, if the aetivated vinyl group is part of a resonance-stabilized system (which has been mentioned already in eonneetion with the stability of BCA). Without stabilisation by a resonance system the substances are too reaetive and unstable, i.e. polymerisation and reactions with components in the surrounding medium, reactions with ammonia and amines taking preeedence (Paulus, 1976). 

In comparision to 2-methyl-4-isothiazolin-3-one (15.1.), the antimicrobial activity of which bases merely on the availability of an activated N-S bond susceptible to nucleophilic attack, the 5-chloro-2-methyl-4-isothiazolin-3-one disposes additionally of a vinyl activated chloro atom and therefore can be characterized as a molecule with two toxophoric structural elements (Paulus, 1988). As a result CMI should exhibit stronger antimicrobial efficacy than the halogen-free MI. This is confirmed by examinations of Diehl and Chapman (1999) see Table 109. Applications for CMI are described under 15.3. 

The aryl ether structure of fluoxastrobin (72 2005, HEC Bayer CropScience) [159] combines a methoximino 5,6-dihydro-l,4,2-dioxazin-2-yl toxophore with an optimally adjusted side-chain bearing a 6-(2-chlorophenoxy)-5-fluoro-pyrimidin-4-yl-oxy moiety as an essentia] element. 

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