Commercial synthetic fungicides structures

Even if the phytoalexins so far isolated have little commercial utility, it is still possible that useful substances may yet appear. But the more exciting possibility is that consideration of the chemical structures of natural phytoalexins and of their modes of action against fungal infections may provide clues for the development of synthetic pesticides. The complexity of the chemical structures of the natural phytoalexins may make them uneconomical to manufacture but a comparison should be made with the synthetic pyrethroid insecticides. The natural pyrethrums have complex chemical structures but simpler compounds, economical to manufacture, have been developed on the basis of the structures of natural pyrethrums and many of these have much more desirable properties for use in agriculture than the natural substances. There would seem to be no reason why simpler compounds based on the structures of natural phytoalexins should not provide synthetic fungicides as important and useful as the synthetic pyrethroids. This is a future challenge for the synthetic organic chemists in this area. 

The useful biological properties of paclobutrazol have inspired further chemical synthesis of azole structures, culminating with the discovery of a series of tertiary alcohol compounds. The original synthetic strategy was conceived as a disconnection and reconnection analysis from paclobutrazol (Figure 5). These early compounds were good fungicides and further optimisation in this area has led to the commercial introduction of two products flutriafol and recently hexaconazole. 

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