Nobel Prize in Chemistry 2021: For the development of Asymmetric Organocatalysis

Benjamin List (Left) and David W.C. (right)

The 2021 Nobel Prize in Chemistry has been given to German scientist Benjamin List of the Max Planck Institute and Scottish-born scientist David W.C. MacMillan of Princeton University “for their contributions to the invention of asymmetric organocatalysis.” Developed by the duo in 2000, this revolutionary method of catalysis is a highly efficient, “precise, inexpensive, rapid, and environmentally friendly” method of developing new compounds.

Building molecules is a difficult art. Benjamin List and David MacMillan are awarded the Nobel Prize in Chemistry 2021 for their development of a precise new tool for molecular construction: organocatalysis. This has had a great impact on pharmaceutical research, and has made chemistry greener.

Press Release- Nobel Prize Committee

What exactly is catalysis?

Catalysis is a term that refers to a reaction that occurs in the presence of a material (the catalyst) that regulates and impacts the reaction’s rate and/or outcome. The substance that assists in accomplishing this – the catalyst — remains intact and is not consumed during the reaction, nor does it become a component of the final product. The catalyst is then removed to avoid impurities being introduced into the final product. Catalysts are frequently employed to synthesise novel and useful compounds that are used in pharmaceuticals and other everyday products. Catalysts in automobiles, for example, convert harmful chemicals in exhaust gases to innocuous compounds. When silver is combined with hydrogen peroxide in a beaker, the latter spontaneously degrades to generate water and oxygen. The silver that triggered the reaction is neither consumed or harmed in any way by the reaction.

According to the Nobel announcement, the eminent Swedish chemist Jacob Berzelius began to notice a trend in 1835. “He cited multiple instances in which the mere presence of a substance initiated a chemical reaction, indicating that this appeared to be a much more common occurrence than previously believed. He believed the material has a catalytic property and coined the term catalysis to refer to the phenomenon.”

Before Asymmetric Organocatalysis

Before Dr. List and Dr. MacMillan discovered the asymmetric organocatalysts, chemists commonly used two very different types of catalysts: metals and enzymes. As the name implies, metal catalysts frequently involve the usage of heavy metals. This not only increases their cost, but also their environmental impact, since appropriate care must be taken to guarantee the final product has no remnants of the catalyst. There are various additional difficulties associated with the use of metal catalysts. Heavy metals utilised in these catalysts are frequently extremely sensitive to oxygen and moisture. As a result, industrial application of this type of catalysts necessitated the use of equipment that insured no contact with oxygen or moisture, which increased the process’s cost.

The issue with enzyme catalysts is their extremely huge size. They are frequently 10,000 times larger than the actual target medication and can take the same amount of time to manufacture. Enzymes, which are naturally occurring proteins, are excellent catalysts. Additionally, our bodies contain thousands of such enzyme catalysts that aid in the formation of essential chemicals for life. Numerous molecules are mirror versions of one another — left-handed and right-handed. However, the molecules of interest will be a mirror image of one of the two. Numerous enzymes catalyse in an asymmetric fashion, resulting in the formation of a single mirror image. Additionally, they operate in a continuous manner – when one enzyme completes a process, another takes over. This enables them to construct complex molecules with astounding precision.

Asymmetric Organocatalysts vs Metal- and Enzyme-catalyzed reactions

In comparison to enzyme catalysts, asymmetric organocatalysts are composed of a single amino acid. Not only are they environmentally benign, but they also accelerate the reaction and reduce the cost of the procedure. Most crucially, because asymmetric organocatalysts are formed from a single circular amino acid, only one mirror version of the molecule can occur. Chemists frequently require only one of these mirror images, especially when synthesising medicines.

Organic catalysts are composed of a sturdy framework of carbon atoms that can accommodate additional active chemical groups. These are frequently composed of components found in nature, such as oxygen, nitrogen, sulphur, or phosphorus. As a result, these catalysts are both environmentally benign and cost effective to manufacture.

Organocatalysts enable the uninterrupted execution of numerous phases in the molecule manufacturing process. This is accomplished through cascade reactions in which the product of the first reaction serves as the starting material for the subsequent one, obviating the need for extra purification between each reaction step. This contributes significantly to waste reduction in chemical manufacture. Prior to the advent of organocatalysts, it was frequently required to identify and purify each intermediate product in order to avoid the buildup of a huge volume of unneeded byproducts. This resulted in some of the material being lost at each stage of the procedure.

Applications of Asymmetric Organocatalysts

Since the two laureates pioneered the notion of asymmetric organocatalysis, the field has grown exponentially. Since 2000, the field of asymmetric organocatalysis has grown. Numerous inexpensive and stable organocatalysts have been discovered that can be utilised to catalyse a wide variety of chemical processes and applications. This time period is dubbed the ‘organocatalysis gold rush.’ At the moment, the field is “well established in organic chemistry and has expanded into a number of novel and intriguing applications.”

Apart from assisting in the development of novel compounds used in a variety of industries, pharmaceutical companies have employed asymmetric organocatalysis to “simplify the synthesis of existing medications.” They can now carve out the thousands of diverse compounds we use in our daily lives, such as medications, plastics, fragrances, and food flavourings, thanks to a plethora of catalysts that can break down or connect molecules together. According to the release, chemical catalysis contributes to around 35% of the world’s overall GDP in some form.

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