Asymmetric Synthesis

What is an Asymmetric Synthesis?

Chemistry as a subject is spread to a vast context and does not limit itself to a few formulas and chemical names. There is actually more to it than we can imagine. As an instance of this, we are here to give you a glimpse of one such chemical phenomenon that has its role in multiple applications of human life and the environment as a whole, asymmetric synthesis

Asymmetric synthesis, also known as enantioselective synthesis, might at first sound like a complex chemical phenomenon, but to your surprise, it isn't. The term 'asymmetric' in itself tells us that something over here is out of symmetry, but what? Let's find out!

Pertaining to the fact that this phenomenon is circumferenced by chemistry, we may understand this in simpler terms for getting a clear insight. 


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Each compound has multiple molecules, and every molecule has its own structural symmetry. However, when this structural molecule symmetry is disturbed, it acts to affect the compound by transforming it into lopsided segments of compounds. 

As you can expect, these unbalanced proportions further differ in their asymmetrical structures at the central point, which remains the most affected. 

IUPAC has a relatively complicated definition for us in store: It defines this chemical synthesis as a reaction in which one or more new elements of chirality are formed in a molecule that produces stereoisomeric products in unequal amounts. 

The involvement of organic compounds is a prerequisite in most circumstances.  


History of Asymmetric Synthesis

The discovery of enantioselective synthesis can be dated back to the period of the early nineteenth century, 1815, when a French physicist, Jean B. Biot stirred his interest in the topic. He was attracted to the property of optical activity of light, whose nature was later solved by Louis Pasteur in the year 1848. He was bent on giving a name to this property, but he restricted it to defining nature as dissymmetry. 

In the following years, exploration of the word chirality drove all the minds crazy, the term was coined by Lord Kelvin. 

Fast forward to the year 1894, when Hermann E. Fischer came up with the concept of asymmetric induction, which now became the foundational process of asymmetric synthesis. He was successful in conducting studies and performing them practically. 

As a result of his determination, he was undefeated in demonstrating the first-ever inference of asymmetric synthesis. Conclusively, today we know it as the Kiliani-Fischer synthesis. 

While the work of Willy Marckwald in describing the earliest asymmetric synthesis is given eminent historic significance, chemists like J.J Berzelius are known for constantly providing contrasting evidence of Marckwald's explanation. 

History could not record its next development until the beginning of the 1950s. This period saw the amalgamation of successful chemists like Woodward and Prelog, to name a few with the ultimately newly developed techniques. These techniques helped scientists to closely observe the structure, nature, and functioning of asymmetric synthesis. 

Drugs were made and prescribed by physicians to treat morning sickness and similar symptoms, one such drug example is Thalidomide. However, it was an unsuccessful experiment that impacted many young lives negatively. 

Later developments of the twentieth century helped shape asymmetric synthesis whatever it is today. 


Principles of Asymmetric Synthesis

Unlike any other chemical phenomena, asymmetric synthesis has certain principles that direct its working and usage. Some of the most popularly known and advocated fundamentals of asymmetric synthesis partial and absolute include:

  • Stereoselectivity

  • Kinetic and Thermodynamic Control

  • The Iso Inversion Principle

  • Single and Double asymmetric Induction

  • Kinetic Resolution


Quick Facts About Asymmetric Synthesis

The phenomenon of asymmetric synthesis is applied to multiple settings in which we live and that surround us. 

  • The progress of the drug industry is solely dependent on the workings of asymmetric synthesis.

  • Variations in the reaction patterns of all the living systems are attributed to different enantiomers, this is possible because living beings possess a high degree of the property, chirality. 

  • The basis of amino acids and sugars is rooted back in the existence of a mere enantiomer. 

  • New developments in the field of asymmetric synthesis are taking place. One such technological development is known as asymmetric organocatalysis.

This is exactly what the fundamentals of asymmetric catalysis are.


Conclusion

Asymmetric synthesis is a growing topic in the field of chemistry and invites scientists to dig this topic more. With all the available information that we possess about this topic, we can surely say that the underlying principles, applications, and relevance in the real world are inevitable and present everywhere. 

FAQs (Frequently Asked Questions)

1. How Do You Define Asymmetric Synthesis Comprehensively?

Ans: As noted earlier, asymmetric synthesis refers to the impact created on a compound, when the structural symmetry of a molecular compound is interrupted. However, since its very inception, an exact definition of asymmetric synthesis has been ambiguous and constantly under discussion.

In order to make the classification process of asymmetric synthesis easier, certain criteria can be used to judge the phenomenon: 

  • The stereoselective synthesis should formulate a major chunk of this phenomenon.

  • The chiral catalyst loadings are relatively lower.

  • The chiral auxiliary should be recoverable and removable if used at all.

  • Affordable replacement and establishment of both the chiral catalyst as well as chiral auxiliary should be available.

2. What are the Types of Asymmetric Synthesis?

Ans: Multiple compounds are used in the process of asymmetric synthesis as per the principles in use. Based on the used compound, a catalytic asymmetric synthesis can be further understood in four of its types namely:

  1. Substrate controlled asymmetric synthesis

  2. Chiral auxiliary controlled asymmetric synthesis

  3. Reagent controlled asymmetric synthesis

  4. Chiral catalyst controlled asymmetric synthesis 


Irrespective of the compounds used, an asymmetric synthesis is always available in two of its standard types, that is, partial asymmetric synthesis and absolute asymmetric synthesis. Asymmetric synthesis partial and absolute differs from each other only on the use of optically active reagents. While a partial asymmetric synthesis makes use of optically active reagents, the absolute asymmetric synthesis barres the use of the same.

3. What is the Importance of Asymmetric Synthesis?

Ans: The most important usage of the phenomenon of asymmetric synthesis is in the pharmaceutical sector. The Drug industry has been researching actively to get to a suitable match for their needs using asymmetric synthesis. 


Biological systems possess the property of chirality and help biological beings experience varying responses throughout their lives.


Moisturizers and sweeteners use efficient asymmetric synthesis strategies for their very existence.


Overall the importance of asymmetric synthesis is spread across sectors and it is significant to maintain the phenomenon with stability.