Diketopiperazine The formation of aspartimide during peptide synthesis is a significant hurdle that can lead to reduced yields, complex purification processes, and even the inability to synthesize desired peptide sequences. Understanding the mechanisms behind aspartimide formation and implementing effective prevention strategies are crucial for successful peptide chemistry. This persistent challenge, particularly in Fmoc-based solid-phase peptide synthesis (SPPS), arises from the inherent reactivity of aspartic acid residues.
Aspartimide formation is a side reaction that occurs when the beta-carboxyl side chain of an aspartic acid residue reacts with the alpha-carboxyl amide bondSequence dependence of aspartimide formation during 9 .... This intramolecular cyclization results in the formation of a five-membered imide ring, known as an aspartimideAspartimide formation- Aspartimide formation is a side reaction caused by repeated exposure to piperidine or other bases during fmoc SPPS. This can be .... This process is often triggered by exposure to bases, such as piperidine, which is commonly used in Fmoc deprotection steps. The aspartimide intermediate can then undergo ring-opening, leading to either the original alpha-peptide bond or, more problematically, a beta-peptide bond. This epimerization at the alpha-carbon of the aspartic acid residue can significantly alter the peptide's structure and biological activity.
The propensity for aspartimide formation is influenced by several factors, including the peptide sequence, the protecting groups used, the reaction conditions (such as base strength, temperature, and reaction time), and the synthesis methodologythe effects of protecting groups, acid, base, temperature .... Sequences containing aspartic acid adjacent to glycine (Asp-Gly) are particularly prone to this side reaction due to the proximity and flexibility of the residues.Preventing aspartimide rearrangements during fmoc-based ...
Given its detrimental effects on peptide synthesis, numerous strategies have been developed to prevent or minimize aspartimide formation. These approaches target different stages of the synthesis process and aim to either block the reactive sites or modify reaction conditions to disfavor imide formation.
1. Protecting Group Strategies:
One of the most effective methods involves employing specific protecting groups for the aspartic acid side chain. Groups that sterically hinder the cyclization or are less susceptible to cleavage under basic conditions can significantly reduce aspartimide formation2025年8月26日—Aspartimide formationremains a persistent challenge in Fmoc solid phasepeptide synthesis. This review surveys strategies to prevent .... For instance, using bulky protecting groups on the beta-carboxyl of aspartic acid can prevent the nucleophilic attack required for ring closure.ASPARTIMIDE FORMATION Similarly, certain protecting groups on the alpha-nitrogen of the preceding amino acid can also block the formation of the aspartimide.Learn about aspartimide formation in peptide synthesis, its mechanisms, side reactions, and strategies to improve peptide purity and yield.
2.Aggregation, Racemization and Side Reactions Modifying Synthesis Conditions:
Adjusting the conditions under which peptide bonds are formed and deprotected can also mitigate aspartimide formation.
* Base Selection and Concentration: Using milder bases or reducing the concentration and exposure time to strong bases like piperidine during Fmoc deprotection can limit the reactionSequence dependence of aspartimide formation during 9 ....
* Coupling Reagents: Employing slower-acting coupling reagents might reduce the likelihood of side reactions, including aspartimide formation, which is more prevalent during rapid synthesis protocols.The use of the aspartic acid derivatives according to the present invention leads to the minimization of base catalyzedaspartimide formation during peptide...
* Temperature Control: Maintaining lower temperatures during critical steps can also help suppress the formation of unwanted byproductsAspartimide formation during peptide synthesisis a prevalent side reaction that compromises yield and purity, especially in Asp-containing peptides..
* Microwave-Assisted Synthesis: While microwave synthesis can accelerate peptide assembly, it can also exacerbate side reactions. Optimizing microwave parameters and using specific protocols can help control aspartimide formation in these systems.
3. Sequence-Specific Considerations:
For sequences known to be particularly susceptible, such as those containing Asp-Gly or Asp-Asp, specialized approaches may be necessary. This can include using orthogonal protecting group strategies or employing alternative ligation techniques like Native Chemical Ligation (NCL) with careful consideration of "good NCL practices" to limit the formation of aspartimide and its subsequent byproducts.
4. Blocking Groups on the Alpha-Nitrogen:
Incorporating a blocking group on the alpha-nitrogen of the amino acid preceding aspartic acid in the peptide sequence can effectively prevent aspartimide formation by sterically inhibiting the cyclization process.
The primary consequence of aspartimide formation is the generation of unwanted byproducts, which lowers the overall yield of the desired peptideDetection and control of aspartimide formation in the .... These byproducts often include epimerized forms of the peptide, where the aspartic acid residue has been converted to its D-isomer, or peptides with a beta-peptide linkage. Separating these closely related impurities from the target peptide can be extremely challenging and costly, often requiring advanced chromatographic techniques. In some cases, the presence of aspartimide byproducts can render the synthesized peptide unusable for its intended application, especially in pharmaceutical or biochemical research where high purity is paramount.
Aspartimide formation remains a significant challenge in peptide synthesis, particularly in Fmoc SPPS.作者：JP Tam·1988·被引用次数：126—Factors affectingaspartimide formation, such as protecting groups, acidity, basicity, and temperature, were studied using the model tetrapeptide, ... However, a comprehensive understanding of its mechanism, coupled with the strategic application of appropriate protecting groups, optimized reaction conditions, and sequence-specific considerations, allows chemists to effectively suppress or prevent this detrimental side reaction. By carefully selecting methodologies and reagents, researchers can enhance peptide purity and yield, ensuring the successful synthesis of complex peptides and proteins.Aggregation, Racemization and Side Reactions
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