Synthetic chemistry and Lego: building cost effective herbicides from molecular building blocks
Lego is arguably the greatest toy ever invented.
With simple, small building blocks that reliably fit together, we can build very creative and complex structures.
Lego blocks build almost anything. There are only two constraints; imagination and the availability of blocks. For example, if we want to build a six foot dinosaur from Lego, we will need a lot of blocks.
Designing useful herbicides is the same. Agricultural herbicides are high volume products. Today, farmers around the world use almost two million tonnes of herbicides a year1 to protect their harvests from crop-killing weeds. Identifying a new herbicidal molecule that is safe to use and effective at breaking weed resistance is not enough; the molecule must be both scalable and affordable to ensure food security globally. This means thinking about the chemical building blocks we will use to make our new mode of action herbicides. How much do they cost? Are they available on sufficient scale? These are questions we think about early on.
There are different types of Moa chemist designing these new herbicides. We have discovery chemists, who analyse data generated across the company and use this to design new molecules to drive our advanced novel herbicidal mode of action projects forward. We have computational chemists, who apply a range of computational tools to both design new molecules and predict how they may behave. Finally, we have synthetic chemists, who drag these ideas for molecules into reality, providing the first tangible, physical sample of the molecule in the world. Synthetic chemists spend a lot of time thinking about how chemical building blocks can be combined to make these new molecules, both in our own lab and how we will ultimately translate this to a much larger, commercial scale.
By understanding the price and availability of different chemical building blocks, applying some reasonable assumptions and our knowledge of how chemical building blocks can be combined to form new molecules, synthetic chemists can estimate the cost of these new herbicides in $/kg. Combining these final molecule price estimates ($/kg) with weed efficacy data (g/ha), we can understand whether our molecules would be economically attractive to farmers ($/ha) or not. At Moa, we use this information to refine the design of our herbicidal molecules.
As a recent example, we examined a lead molecule within one of our lead novel mode of action projects. We identified parts of the molecule that added three steps to our putative manufacturing route and significant anticipated cost, but we questioned whether it afforded us any efficacy benefit. By designing a simplified molecule, we were able to retain efficacy, but significantly reduce the projected cost of the herbicide to farmers.
In synthetic chemistry, making a molecule requires thinking several steps ahead; what sequence of reactions will result in the production of the target molecule in a useful quantity? Identifying a useful herbicide requires similar foresight. The herbicidal molecule must be safe for humans and the environment, effective at controlling weeds and importantly, produced economically at sufficient scale. These requirements can be considered at an early stage.
If this interests you, please get in touch: we’re adding to our synthetic chemistry team!
Sources
1 FAOSTATÂ Â Global herbicide consumption 2022