O-acylisourea

Definition

O-acylisourea is an important reactive intermediate that arises in various organic reactions, particularly in the context of alcohol reactions, acid anhydride chemistry, and peptide synthesis. It serves as a key coupling agent, facilitating the formation of new bonds and enabling the transformation of starting materials into desired products.

5 Must Know Facts For Your Next Test

1. O-acylisourea is formed as an intermediate when a carboxylic acid is activated by a carbodiimide, such as DCC (dicyclohexylcarbodiimide) or EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide).
2. The O-acylisourea intermediate is highly reactive and can undergo nucleophilic attack by alcohols, leading to the formation of esters in the Steglich esterification reaction.
3. In the context of acid anhydride chemistry, O-acylisourea can be formed as an intermediate when an acid anhydride reacts with a nucleophile, such as an alcohol or amine.
4. In peptide synthesis, O-acylisourea plays a crucial role in the formation of amide bonds between amino acids, facilitating the coupling of the carboxyl group of one amino acid with the amino group of another.
5. The reactivity and instability of the O-acylisourea intermediate make it a valuable but challenging species to work with, often requiring careful reaction conditions and monitoring to ensure the desired transformation occurs.

Review Questions

• Explain the role of O-acylisourea in the Steglich esterification reaction, and describe the key steps involved in this process.
  • In the Steglich esterification reaction, O-acylisourea is formed as a reactive intermediate when a carboxylic acid is activated by a carbodiimide, such as DCC or EDC. The O-acylisourea then undergoes nucleophilic attack by an alcohol, leading to the formation of an ester product. The key steps involve the initial activation of the carboxylic acid, the generation of the O-acylisourea intermediate, and the subsequent reaction with the alcohol to form the desired ester. This reaction is particularly useful for the synthesis of sterically hindered esters that may be difficult to prepare using other methods.
• Describe the role of O-acylisourea in the chemistry of acid anhydrides, and explain how it can be utilized in the transformation of these starting materials.
  • In the context of acid anhydride chemistry, O-acylisourea can be formed as an intermediate when an acid anhydride reacts with a nucleophile, such as an alcohol or amine. The formation of the O-acylisourea intermediate facilitates the transformation of the acid anhydride into other useful products. For example, the reaction of an acid anhydride with an alcohol in the presence of a carbodiimide can lead to the formation of an ester, where the O-acylisourea acts as a coupling agent. Similarly, the reaction of an acid anhydride with an amine can result in the formation of an amide, with the O-acylisourea playing a crucial role in the coupling process.
• Discuss the importance of O-acylisourea in peptide synthesis, and explain how its reactivity and instability contribute to the challenges and considerations in this area of organic chemistry.
  • In peptide synthesis, O-acylisourea is a critical intermediate that facilitates the formation of amide bonds between amino acids. The high reactivity of the O-acylisourea species allows it to couple the carboxyl group of one amino acid with the amino group of another, enabling the assembly of the peptide chain. However, the instability of the O-acylisourea intermediate presents challenges in peptide synthesis, as it must be generated and reacted under carefully controlled conditions to ensure the desired transformation occurs. The reactivity of O-acylisourea also necessitates the use of specific coupling agents, such as carbodiimides, and the consideration of side reactions that may compete with the desired peptide bond formation. Navigating these complexities is a key aspect of successful peptide synthesis in organic chemistry.

Related terms

Carbodiimide:

A class of organic compounds containing a carbon-nitrogen-nitrogen functional group, commonly used as coupling agents in organic synthesis.

Acylation:

The process of introducing an acyl group (R-C=O) into a molecule, often resulting in the formation of esters, amides, or other derivatives.

Peptide Bond:

A covalent bond formed between the carboxyl group of one amino acid and the amino group of another, linking them together in a peptide or protein chain.