Chemists Broke A 100-Year-Old Rule, And It Could Lead To Making New Kinds Of Medicine
In the early 20th century, a German chemist named Julius Bredt studied double bonds in bicyclic molecules, which are a group of chemicals that contain two ring-shaped structures attached together.
The shape of these bicyclic molecules looks something like a three-dimensional Y-shaped structure. According to Bredt’s rule, based on his observations in the lab, carbon atoms next to the “Y” junctions cannot form double bonds.
Since the carbon near the Y-shaped bridges and its surrounding atoms are not all in the same plane, Bredt believed that a double bond at the bridgehead position would make the molecule too unstable to exist.
But now, a team of chemists from the University of California, Los Angeles, have broken this 100-year-old chemistry rule by synthesizing a class of molecules that were thought to be too unstable to form.
The “anti-Bredt” molecules violate Bredt’s rule. They could help further drug research and allow scientists to make new kinds of medicine.
“If there’s a rule that says something is absolutely impossible, then maybe you just haven’t thought of the right way of solving it. And if you do it, it actually might not be as difficult as you think,” said Luca McDermott, the first author of the study and an organic chemist at UCLA.
The anti-Bredt molecules belong to a class of compounds called olefins, which have at least one double bond connecting two carbon atoms.
A double bond is a strong chemical bond made from two pairs of electrons. Each of the carbon atoms is usually present in the same two-dimensional plane as the other atoms they’re bonded to.
McDermott and colleagues figured out how to make anti-Bredt olefins and are using the method to synthesize complex three-dimensional molecules.
ImageFlow – stock.adobe.com – illustrative purposes only – pictured above is a colorful molecule model
Since the anti-Bredt olefins are highly reactive and unstable, the team was unable to directly isolate them.
Instead, they added other molecules that could react immediately with the anti-Bredt olefins and form more stable products.
That way, they could experiment with a wide variety of anti-Bredt olefins and their more stable products.
These reactions could pave the way for the development of new types of medicines. The stiff three-dimensional structures could better interact with proteins in the body.
Anti-Bredt olefins have not been explored in-depth until now because people believe that Bredt’s rule is set in stone.
But it should really be viewed as a guideline that may be possible to overcome so as not to inhibit creativity.
“If we can question Bredt’s rule after 100 years and push the limits of it, there’s probably all sorts of other rules that are waiting to be reexamined,” said UCLA professor and chemist Neil Garg, a co-author of the study.
The research was published in the journal Science.
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