Aspartimiderearrangement 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.Aspartic acid derivatives - Patent 2886531 Understanding the mechanisms behind aspartimide formation and implementing effective prevention strategies are crucial for successful peptide chemistryEP2886531A1 - Aspartic acid derivatives - Google Patents. 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 bond. This intramolecular cyclization results in the formation of a five-membered imide ring, known as an aspartimide.作者：JL Lauer·1995·被引用次数：158—We have examined the sequence dependence ofaspartimide formationduring Fmoc-based solid-phase synthesis of the peptide Val-Lys-Asp-X-Tyr-Ile. 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 methodology. 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.Identification, occurrence and prevention of aspartimide ...
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作者：D Flora·2005·被引用次数：31—A method was developed to diagnose and minimizeaspartimide formation during the synthesis of cyclic peptides on solid phase. Peptide 2 was prepared with ....
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 formation作者：MJW Kong·2025·被引用次数：2—Aspartimide formation remains a persistent challenge in Fmoc solid phase peptide synthesis. This review surveys strategies to prevent aspartimide formation, .... For instance, using bulky protecting groups on the beta-carboxyl of aspartic acid can prevent the nucleophilic attack required for ring closure.Aspartimide formation during peptide synthesisis a prevalent side reaction that compromises yield and purity, especially in Asp-containing peptides. Similarly, certain protecting groups on the alpha-nitrogen of the preceding amino acid can also block the formation of the aspartimide.
2. 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 reaction.
* 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.
* Temperature Control: Maintaining lower temperatures during critical steps can also help suppress the formation of unwanted byproducts.
* Microwave-Assisted Synthesis: While microwave synthesis can accelerate peptide assembly, it can also exacerbate side reactionsMeasures to Prevent Aspartimide Formation. Optimizing microwave parameters and using specific protocols can help control aspartimide formation in these systems.
3.2021年8月25日—Aspartimides are formed upon ring-closurebetween the nitrogen of the alpha-carboxyl amide bond and the beta-carboxyl sidechain and subsequent ... Sequence-Specific Considerations:
For sequences known to be particularly susceptible, such as those containing Asp-Gly or Asp-Asp, specialized approaches may be necessary.A Systematic Comparison of Different Methods to Tackle ... 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 peptide作者：E Nicolás·1989·被引用次数：149—Piperidine showed a marked tendency to form aspartimidesduringFmoc deprotection. The behaviour of protected H Val Lys Asp Gly Tyr Ile OH towards imide .... 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. 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.
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