Ligands Go Chiral!

Scientists, specifically Baihua Ye and Nicolai Cramer added biotin to a cyclopentadienyl ring, functionalized it with rhodium, and attached it to the protein streptavidin. What does this all do? This complex allows them to perform rhodium catalyzed reactions to make single-enantiomer products, or products with a single conformation. This is very important to scientists since it allows them to get products that they desire, as as we all know, a little change in structure results in a big change. Here is a link of an image of what is being described

 

You can see in the picture that a ring is attached to Rhodium--that is the catalyst. Furthermore, the Rh is connected to Streptavidin which is then connected to biotin. This may seem very complicated, which it is, the point is that the conformation in this picture is what makes the complex useful. It works like an enzyme, a lock and key like structure. Once again, this we see the connection of transmetal catalysts to biology and specifically enzymes. One may think that since enzymes are catalysts, that it isn't out of the ordinary for there to be such a connection between enzymes and transition metal catalysts. However, it is very hard to join these things together, as seen in our previous posts about the rhodium catalyst as well. So don't take this as a walk in the park. The emergence of organocatalysts are no minor thing in the timeline of chemistry.