OxymaPure DIC in Peptide Coupling: Mechanism, Efficiency, and Safety
Efficient and Safe Peptide Bond Formation Using OxymaPure DIC Coupling
OxymaPure DIC peptide coupling is widely used in peptide synthesis due to its efficiency and low racemization. This method involves the activation of the carboxyl group by DIC, followed by OxymaPure-mediated ester formation, which facilitates amide bond formation with minimal side reactions.
Traditional methods employing diisopropylcarbodiimide (DIC) alone have been associated with significant racemization of amino acids, compromising the integrity of the synthesized peptides. The introduction of additives like OxymaPure [ethyl 2-cyano-2-(hydroxyimino)acetate] has revolutionized this process by enhancing coupling efficiency and minimizing racemization.
The OxymaPure DIC combination is now widely recognized as a superior method in both solid-phase and solution-phase peptide synthesis
| Property | OxymaPure | HOBt | 6-Cl-HOBt | HOAt |
|---|---|---|---|---|
| pKa | 4.60 | 4.60 | 3.35 | 3.28 |
| M [Da] | 142.11 | 135.11 | 169.57 | 150.13 |
| CAS | 3849-21-6 | 2592-95-2 | 26198-19-6 | 39968-33-7 |
Mechanism of OxymaPure DIC Peptide Coupling
The coupling mechanism begins with the activation of the carboxylic acid by DIC, forming an O-acylurea intermediate. This intermediate is prone to side reactions, including racemization and the formation of by-products. The addition of OxymaPure addresses these issues effectively.
The anionic form of OxymaPure reacts with the O-acylurea, releasing N,N’-diisopropylurea and forming a more reactive OxymaPure ester. This activated ester readily undergoes aminolysis with the nucleophilic amine, leading to the desired amide bond formation while regenerating OxymaPure. This process not only enhances coupling efficiency but also significantly reduces racemization.
Advantages in Solid-Phase Peptide Synthesis (SPPS)
In SPPS, the OxymaPure DIC system offers several advantages over traditional methods. Notably, it provides higher coupling efficiencies and lower racemization rates compared to additives like HOBt, 6-Cl-HOBt, and HOAt, which have been associated with explosive hazards.
OxymaPure is non-explosive, making it a safer alternative without compromising performance. Studies have demonstrated its effectiveness in both manual and automated peptide synthesis, including microwave-assisted protocols. Furthermore, OxymaPure exhibits high solubility in common peptide synthesis solvents, facilitating its integration into various synthetic workflows. Moreover, OxymaPure plays an important role in preventing aspartimide side reaction.
Considerations Regarding Hydrogen Cyanide Formation
Recent studies have reported that the reaction between OxymaPure and DIC can generate trace amounts of hydrogen cyanide (HCN). While the quantities are minimal, appropriate safety measures should be implemented to mitigate any potential risks.
It is advisable to conduct couplings in well-ventilated areas and consider the use of scavengers or alternative solvents to minimize HCN formation. Additionally, the technique to scavenge the generated HCN with DMTS was reported, as well as the solvents in which this reaction is slowed down.
Despite this consideration, the benefits of using OxymaPure DIC in peptide synthesis remain substantial, provided that standard laboratory safety protocols are followed.
Conclusion
The OxymaPure DIC coupling system stands out as an efficient and safer alternative for peptide bond formation, addressing the challenges of racemization and hazardous by-products associated with traditional methods. Its application in both solid-phase and solution-phase peptide synthesis has been well-documented, offering high yields and purity. Ongoing research continues to optimize its use and explore new derivatives to further enhance peptide synthesis methodologies.
References
Development and Mechanism of OxymaPure in Peptide Coupling
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Safety and Hazardous Properties of Traditional and New Coupling Reagents
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Applications of OxymaPure in Peptide Synthesis and Beyond
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Ma, Y., Liu, Y., Wang, J., Chen, X., Yin, H., Chi, Q., Jia, S., Du, S., Qi, Y., Wang, K. (2022). DIC/Oxyma-Based Efficient Synthesis and Activity Evaluation of Spider Peptide Toxin GsMTx4. Chinese Journal of Organic Chemistry, 42(2), 498-506.
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Advances in Peptide Coupling Reagents and Structural Considerations
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El-Faham, A., Al Marhoon, Z., Abdel-Megeed, A., Albericio, F. (2013). OxymaPure/DIC: An Efficient Reagent for the Synthesis of a Novel Series of 4-[2-(2-Acetylaminophenyl)-2-Oxo-Acetylamino] Benzoyl Amino Acid Ester Derivatives. Molecules, 18(12), 14747–14759.
- Demonstrates the application of the OxymaPure/DIC system in synthesizing complex amino acid derivatives, highlighting its efficiency and versatility beyond standard peptide coupling.
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