Chemists succeed in synthesis of aminoalcohols by utilizing light
Whether in beta-blockers for the treatment of hypertension or in natural products, the so-called surrogate amino alcohols are high-quality organic compounds that are found in many everyday products. However, they are very difficult to produce, and chemists have long been trying to develop efficient methods for their synthesis. In research recently published in the journal Nature Catalysis, scientists led by Prof. Dr. Frank Glorius at the University of Münster have found a solution for the production of a special variant of amino alcohols. Glorius, from the Institute of Organic Chemistry at the University of Münster, emphasizes that "the new method helps to study the properties of the substance and to find applications for these new compounds in the future".
Vicinal aminoalcohols can appear in two different variants, the so-called regioisomers, in which the amine and alcohol functional groups exchange positions. Although they are thus very similar, they usually have different biochemical properties. Installing both amine and alcohol groups in one step is a major challenge. The discovery of asymmetric amino hydroxylation reactions, in which one of the substituted isomers was created, even led to the Nobel Prize awarded to chemist Barry Sharpless in 2001. Yet, another isomer could not be synthesized in a similar way and has been a long-standing problem - until now. With the help of a new photoinitiated reaction method by chemists, the synthesis of the other isomer is now also becoming effective.
Unactivated olefins containing carbon-carbon double bonds are known as feedstock chemicals for reaction processes due to their good availability. Generally, through such carbon-carbon double bonds of inactive alkenes both amine and alcohol groups are installed in one step, starting at any time with the amine group and then adding the alcohol group. Thus, a specific substituted amino alcohol isomer is always formed. Now, scientists have discovered a special class of amine compounds that are reactive, yet stable enough to allow the addition of an alcohol group to a carbon-carbon double bond followed by an amine group to generate enantiomeric isomers of substituted amino alcohols that were previously unavailable.
"Just as plants use chlorophyll to convert light into energy, we are using what is called a photocatalyst," explained Dr. Tuhin Patra, the study's first author." This species absorbs light from the blue LED and transfers its energy to molecules directly involved in the reaction. This releases both amines and alcohol groups." This process of transferring electrons between molecules to each other is known as energy transfer, the scientists explain.
Intriguingly, the new method generates the least accessible regioisomers of the substituted amino alcohols in such a way that the alcohol and amine groups are protected from further reactions. Depending on the needs of the user, one of the two alcohol or amine groups can now be reactivated without affecting the other one. However, if this is necessary for further requirements of the synthesis, it is even possible to have both groups reacted further at the same time." Previous designs typically installed only one group at a time in a complex multi-step overall process. Our design allows not only to install two different groups in one step and obtain the required protection, but also to reliably generate the least accessible regioisomers, providing an opportunity to investigate future applications of such compounds." Glorius concluded.
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