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Ryan Spencer Shinabery, Soumitra Maity, and Nan Zheng (from left) have created a new, "green" method for developing medicines. (Not shown: Mingzhao Zhu.) Photo: University of Arkansas
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A team of University
of Arkansas researchers has
created a new, "green" method for developing medicines. The researchers used
energy from an ordinary 13-W compact fluorescent light bulb to create an
organic molecule that may be useful in the treatment of Alzheimer’s and other
brain diseases. The finding, coauthored by Soumitra Maity, Mingzhao Zhu, Ryan
Spencer Shinabery, and Nan Zheng, is published in Angewandte Chemie International
Edition.
"Our chemical reaction provides a new structure, a new building block for
pharmaceutical companies that has not been available before," said Zheng, an
assistant professor of chemistry in the J. William Fulbright College of Arts
and Sciences who leads the team. "It's a very unusual scaffold, very lipophilic
and non-polar, which is what you need to cross the blood brain barrier."
Visible-light photocatalysis, or chemical reactions sparked by visible
light, are rare in organic chemistry, because most organic compounds can’t
readily absorb visible light. Instead, organic chemists typically rely on
ultraviolet, or UV light, which has disadvantages.
"UV lights heat up very fast and waste a lot of energy. You'll also get a
sunburn if your skin is exposed," said Shinabery, a senior honors chemistry
student.
Postdoctoral student Mingzhao Zhu initiated the research with his effort to
use light from a cheap, readily available light source—a supermarket light
bulb, in this case, although sunlight would work just as well—to make an
organic molecule useful to chemists. Using ruthenium, a metal that is active in
the presence of visible light, as a catalyst, Zhu produced an unexpected and
unstable organic molecule. Shinabery subsequently worked to identify the
structure of the molecule.
"Spencer was able to reproduce the result and help us understand how the
molecule was formed, which we needed to design a new reaction," Zheng said.
Maity, also a postdoctoral student, led the way in developing the new
reaction, which is green thanks to efficiency as well as use of visible light.
"All of the atoms are converted to the product. There is no waste, no
additives or co-catalysts, which makes the reaction very clean and atom
economical," Maity said. Maity also succeeded in crystallizing one of the
products, in effect sketching out its 3D structure, which is critical should it
be further developed in pharmaceutical applications.
Zheng and Maity are currently working on a new, even more powerful result:
the use of a catalyst with visible light to create a carbon-nitrogen bond, one
of the most common and important bonds used in pharmaceuticals and materials.
"People thought carbon-nitrogen bonds couldn't be formed this way; this will
change people's perception of visible light photochemistry," Zheng said.
"I am working at all hours," Maity added. "I lose track of time, because the
work is so exciting."
As for Shinabery, he is writing up his contribution to the finding as his
senior honors thesis and weighing multiple offers from top graduate schools.
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