The term Green Chemistry implies that we are using natural products from plants, bacteria, fungi, or animal sources. The development of green pesticides starts with the design of the compounds. Synthetic compounds that are designed off nature's chemistry are termed "biorational" compounds. Once a need for improved "green" pesticides has been identified, the process of design begins, with many green principles in mind.
1. Natural products can be screened to identify the best lead molecule or molecules.
2. Target market can be identified.
3. Determining the characteristics of the natural lead molecule.
4. Develop improvement strategies: to increase efficacy, lengthen the residual time, enhance safety to non-targets, etc.
5. Consider synthesizing derivatives that incorporate the lead molecule into the biorational molecule. Maintain green principles.
6. Consider synthesizing analogs that substitute certain functionalities or groups for moieties extant in the lead molecule. Maintain green principles.
7. Test series of closely-related biorational compounds for obvious trends in efficacy or other important criteria.
8. Develop structure-activity relationships (SAR) or quantitative structure-activity relationships (QSAR).
9. Toxicology considerations, i.e., potential hazards that could be encountered in mammalian testing for LD₅₀ or other toxicology endpoints.
10. Find out if patent protection is feasible for the most desirable of the biorational molecules?
11. Determine if there would be any likely special challenges in the formulation of the best molecules.
12. Investigate costs of starting materials, the number of steps in synthetic route, etc.
13. Assess commercial opportunity viz. available space in the market versus competitors' products.

Greener pesticides of many types are finding their place in the market when potency, safety, and persistence are acceptable. Greener design, environmental degradability, favorable ecotoxicology, and safety to non-target species have become very important principles for the design and development of sustainable agrochemical products.

Colin Wong

Iowa State University

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