**5. Conclusions**

114 Herbicides – Properties, Synthesis and Control of Weeds

determining the activity of PPO inhibitors. The stronger the ability of the carbonyl group to

5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

Actual(pI50)

Fig. 13. Calculated pI50 (Y-axis) are versus actual pI50 (X-axis) values. The dots represent

accept electrons from receptor, the higher the activity of PPO inhibitor.

Fig. 12. Alignment of 37 HTSB compounds.

5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5

training compounds.

Calculated(pI50)

HTSB herbicides are characterised with their high herbicidal activities, fast acting, and environmentally benign. However, most of them cause short-term damage to the crops applied, which makes them no significant market share in the last 30 years (Qasem, 2011).

In recent years, the development of Protox inhibitor-resistant crops (Li and Nicholl, 2005; Vencill, 2011) began a new era for the use of Protox herbicides. Furthermore, weed shifts observed in genetically modified crops, caused by the development of weed resistance to the widely used glyphosate herbicide, will offer market opportunities for herbicides with other modes of action, such as Protox inhibiting herbicides. So, Protox inhibiting herbicides will continue to be an important area of interest to agrochemical companies, with most efforts focused on fine tuning the 5 position of the phenyl ring. The application of CoMFA approach will seed up the discovery processes.
