Chemists achieve breakthrough: Editing molecules instead of rebuilding them

For more than a hundred years, chemists have been building complex molecules step by step – bond by bond, atom by atom. But what if, instead of painstakingly reassembling molecules, they could be directly "rewritten"? This is exactly what a research team led by organic chemist Nuno Maulide from the University of Vienna has now achieved. In a recently published paper, the researchers describe a method that allows one of the most important classes of molecules in chemistry – called N-methylamines – to be directly and selectively transformed into significantly more complex structures. This lays the foundation for modern drug research: with the new method, hundreds of variants of a molecule can be easily prepared. The work was published in Nature Chemistry.

"Amines are everywhere. Proteins, drugs, neurotransmitters – practically all biological processes depend on amines. This makes the ability to directly and selectively modify such structures all the more important," says Uroš Vezonik, a PhD student in the Maulide group at the University of Vienna and co-first author of the study. "Amines, with their special properties, are essential components of all structures of life. And because organisms interact so well with amines, non-natural amines also often have a significant impact on biological systems," adds Nuno Maulide.

Editing molecules instead of rebuilding them 

At the heart of the work is a problem that has occupied synthetic chemistry for decades: the selective modification of so-called secondary N-methylamines, compounds in which a nitrogen atom (amine) carries a methyl group (CH₃). These structures are found in countless pharmaceuticals and biologically active molecules.

Until now, their targeted modification usually required complex multi-step syntheses or the use of sensitive metal catalysts. The new method takes a fundamentally different approach: instead of completely rebuilding complex molecules, only a small part of the molecule is exchanged – a kind of molecular "text correction." For this, the researchers use simple alkenes, readily available hydrocarbon compounds, to directly replace the methyl group of an amine with significantly more complex fragments. The team refers to this principle as "Alkyl Swap." "What's fascinating is the simplicity," explains Daniel Kaiser from the University of Vienna, a co-author of the study. "You can modify highly complex molecules at a very specific point without touching the rest of the molecule."

"Bathtub chemistry" – new reaction under surprisingly mild conditions 

Particularly remarkable is the robustness of the reaction. Many modern methods for functionalizing amines require strictly water- and oxygen-free conditions, special photocatalysts, or sensitive reagents. The new reaction, on the other hand, works under surprisingly simple conditions – and is therefore referred to by Maulide as "bathtub chemistry." "The reaction is so simple that, in theory, you could even do it in a (heatable) bathtub," Maulide explains. "Of course, we still recommend a lab," he jokes.

Giulia Iannelli, co-first author and former postdoctoral researcher in the Maulide group, confirms: "This allows us to functionalize complex amines that could not be transformed in this way with any other known method. That’s what makes this process so valuable."

Breakthrough for modern drug research 

To demonstrate the power of the method, the team tested the reaction on a variety of pharmacologically relevant molecules. These included derivatives of well-known drugs such as fluoxetine, duloxetine, sertraline, atomoxetine, and citalopram. Additionally, they successfully synthesized several commercially important drugs in just a single reaction step.

The method also proved suitable for the late-stage modification of complex drug molecules, peptide functionalization reactions, the synthesis of peptide-drug conjugates, and the rapid production of medically relevant molecular libraries. In modern drug research, where hundreds of variants of a molecule often need to be tested, this strategy could offer significant advantages.

A new way of thinking in synthetic chemistry 

The significance of this work lies not only in the specific reaction but also in the underlying logic. While classical amine syntheses typically rely on aldehydes and reducing agents, the new method uses simple alkenes as stable and readily available starting materials.

"What excites us most is the new way of thinking that this method enables," says Maulide. "Suddenly, molecules that were previously extremely difficult to synthesize become much more accessible." What looks deceptively simple on paper – an amine, an alkene, and formaldehyde in a reaction vessel—could thus establish itself as a significant step forward for modern molecular editing.

Summary: 

• Chemists at the University of Vienna have achieved a breakthrough in modern drug discovery. Instead of synthesising different variants of molecules from scratch for testing, they can now be modified in a targeted manner.
• Using the new method, so-called N-methylamines, one of the most important classes of molecules in chemistry, can be directly and specifically converted into significantly more complex structures.
• To do this, the researchers use simple alkenes, readily available hydrocarbon compounds, to replace the methyl group of an amine directly with significantly more complex fragments. 
• In modern drug discovery, where hundreds of variants of a molecule often need to be tested, this strategy could offer considerable advantages.

About the University of Vienna: 

At the University of Vienna, curiosity has been the core principle of academic life for more than 650 years. For over 650 years the University of Vienna has stood for education, research and innovation. Today, it is ranked among the top 100 and thus the top four per cent of all universities worldwide and is globally connected. With degree programmes covering over 180 disciplines, and more than 10,000 employees we are one of the largest academic institutions in Europe. Here, people from a broad spectrum of disciplines come together to carry out research at the highest level and develop solutions for current and future challenges. Its students and graduates develop reflected and sustainable solutions to complex challenges using innovative spirit and curiosity.