Process to customize molecules does double duty
Inspired by your liver and activated by light, a chemical process developed in labs at Rice University and in China holds great promise for drug design and the development of unique materials.
Researchers led by Rice chemist Julian West and Xi-Sheng Wang of the University of Science and Technology of China, Hefei, report their successful catalytic process of simultaneously adding two different functional groups to single alkenes, organic molecules derived from petrochemicals that at least one carbon-carbon double bond combined with hydrogen atoms.
Better yet, they say, is that these alkenes”not activated– that is, they lack reactive atoms near the double bond – and so far it has proved challenging to improve.
The chemical pathway described in the Journal of the American Chemical Society could simplify the creation of a precursor library for the pharmaceutical industry and improve polymer production.
West, whose lab designs synthetic chemical processes, said the first inspiration came from an enzyme, cytochrome P450, which the liver uses to eliminate potentially harmful molecules.
“These enzymes are like buzzsaws that grind up molecules before they can get you in trouble,” he said. “They do this through an interesting mechanism called radical rebound.”
West said P450 finds carbon-hydrogen bonds and removes the hydrogen, leaving behind a carbon-centered radical that contains an unpaired electron.
“That electron really wants to find a partner, so the P450 will immediately return an oxygen atom (the ‘rebound’), which oxidizes the molecule,” he said. “In the body, that helps to deactivate these molecules so you can get rid of them.
“This kind of rebound is powerful,” West said. “And Harry (lead author Kang-Jie Bian, a Rice graduate student) wondered if we could do something like that to transfer different snippets onto that radical.”
Their solution was to enable what they call radical ligand transfer, a common method that uses manganese to catalyze the ‘radical rebound’.
West said that while P450 uses the nearby element iron to catalyze the biological reaction, previous experiments in the Rice lab and elsewhere have shown that manganese had potential.
“Manganese helped the process be more selective and a bit more active, but also much cheaper and easier,” he explained. “It can transfer a lot of different atoms, such as chlorine, nitrogen and sulfur, just by changing which commercial ingredient you add to the reaction.”
That reaction resulted in one functionalization. Why not go for two?
West said Bian also came up with the idea of adding a photocatalyst to the mix. “If you shine a light on it, it gets excited and you can do things that would be impossible in the ground state, such as activating small fluorocarbon molecules to make radical fragments with carbon-fluorine bonds, which are important for pharmaceutical and materials science. ” he said. “Now we can attach it to our molecule of interest.”
The end result is a mild and modular process of adding two functional groups to one alkene in one step.
“First we have the carbon-carbon double bond of a molecule of interest, the alkene,” West said, summarizing. “Then we add this valuable fluorocarbon, and then the manganese catalyst swims up and does this radical ligand transfer to add a chlorine or nitrogen or sulfur atom.”
He noted that the collaboration between Rice and Wang’s lab was a natural result of Bian’s move to Rice from Hefei, where he received his master’s degree. “We really focused on the manganese aspect of this work, and Wang’s group not only brought expertise in photocatalysis, but also developed and tested carbon fluorine fragments, and showed that they would work very well in this system,” West said.
He said that in addition to the pharmaceutical and materials sciences, chemical biology could also benefit from the process, mainly because of its affinity with: pClicka method discovered by Rice chemist Han Xiao to attach drugs or other substances to antibodies.
Co-authors are Rice undergraduate David Nemoto Jr. and graduate student Shih-Chieh Kao, and Yan He and Yan Li of Hefei. Wang is a professor at Hefei. West is the Norman Hackerman-Welch Young Investigator and an assistant professor of chemistry.
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Kang-Jie Bian et al, Modular difunctionalization of unactivated alkenes by bio-inspired radical ligand transfer catalysis, Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c04188
Quote: Process to customize molecules does double work (2022, June 22) retrieved June 22, 2022 from https://phys.org/news/2022-06-customize-molecules-duty.html
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