Enantiomeric molecules resemble each other like right and left hands. Both variants normally arise in chemical reactions. But frequently only one of the two forms is effectual in biology and medicine. Hitherto, completely converting this mixture into the desired enantiomer was deemed impossible. Deploying a photochemical method, a team from the Technical University of Munich (TUM) has now achieved this feat.
Producing active ingredients with very specific properties – antibacterial characteristics, for example – is not always so easy. The reason: many of these organic compounds are chiral. They have two mirror-image forms, so-called enantiomers.
The allenic group of the unwanted enantiomer is much closer to the thioxanthone sensitizer and is therefore converted to the desired form.
Image: S. M. Huber and A. Bauer / TUM
This small difference can be consequential because the two enantiomers can have different properties. While one has a healing effect, the other might be ineffective or even cause unwanted side effects.
Saving time, energy and resources
"For a long time, researchers around the world have been seeking ways to selectively synthesize only the desired enantiomer from a racemate," explains Prof. Thorsten Bach, holder of the Chair of Organic Chemistry at the Technical University of Munich. However, this has been very difficult, since chemical reactions usually produce both molecule variants.
Together with his team, the researcher has now developed a method with which the desired enantiomer can be obtained from a racemate, the mixture of both enantiomers, in high concentrations of up to 97 percent.
Rather than painstakingly extracting the unwanted mirror-molecules from the mixture, the researchers use a photochemical reaction to transform them into the desired end product. "That saves time, energy and resources because all the molecules are used and you do not need to throw away half of them," explains Bach.
A catalyst for the "right" compounds
The secret of the transformation is a special photochemical catalyst. Originally, the thioxanthone sensitizer was developed for [2 + 2] photocycloadditions. The dye is itself chiral and therefore specifically converts only one of the enantiomers to the other. In the span of a few minutes, the equilibrium shifts in favor of the desired molecule. The undesirable mirror images disappear.
The chemists have successfully tested their new method on various molecular mixtures from the allene structural class. "We could thus demonstrate that selective and efficient catalysis to prepare enantiopure compounds from racemates is fundamentally possible," said Bach.
The project was funded by the German Research Foundation (DFG) as part of the Research Training Group GRK 1626, a Reinhart Koselleck project and the Cluster of Excellence RESOLV. Cooperation partners were the universities of Bonn and Bochum.
Prof. Dr. Thorsten Bach
Chair of Organic Chemistry I
Technical University of Munich
Lichtenbergstr. 4, 85748 Garching
Tel. + 49-89-28913330 – E-mail: email@example.com
Catalytic deracemisation of chiral allenes enabled by sensitised excitation with visible light,
Alena Hölzl-Hobmeier, Andreas Bauer, Alexandre Vieira Silva, Stefan M. Huber, Christoph Bannwarth, Thorsten Bach
Nature, 564, 240–243 (2018) – DOI: 10.1038/s41586-018-0755-1
https://www.tum.de/nc/en/about-tum/news/press-releases/detail/article/35146/ Link to the press release
http://www.oc1.ch.tum.de/index.php?mID=home&mSC=0&mLang=en Link to the homepage of the Chair of Organic Chemistry I
Dr. Ulrich Marsch | Technische Universität München
Towards better anti-cancer drugs: New insights into CDK8, an important human oncogene
28.01.2020 | Universität Bayreuth
Unique centromere type discovered in the European dodder
28.01.2020 | Leibniz Institute of Plant Genetics and Crop Plant Research
Researchers from Dresden and Osaka present the first fully integrated flexible electronics made of magnetic sensors and organic circuits which opens the path towards the development of electronic skin.
Human skin is a fascinating and multifunctional organ with unique properties originating from its flexible and compliant nature. It allows for interfacing with...
Researchers of the Carl Gustav Carus University Hospital Dresden at the National Center for Tumor Diseases Dresden (NCT/UCC), together with an international...
A Duke University research team has identified a new function of a gene called huntingtin, a mutation of which underlies the progressive neurodegenerative...
For years, a new synthesis method has been developed at TU Wien (Vienna) to unlock the secrets of "strange metals". Now a breakthrough has been achieved. The results have been published in "Science".
Superconductors allow electrical current to flow without any resistance - but only below a certain critical temperature. Many materials have to be cooled down...
KIT researchers develop novel composites of DNA, silica particles, and carbon nanotubes -- Properties can be tailored to various applications
Using DNA, smallest silica particles, and carbon nanotubes, researchers of Karlsruhe Institute of Technology (KIT) developed novel programmable materials....
16.01.2020 | Event News
15.01.2020 | Event News
07.01.2020 | Event News
28.01.2020 | Life Sciences
28.01.2020 | Materials Sciences
28.01.2020 | Health and Medicine