Alpha- and beta- aspartyl peptide ester formation via aspartimide ring opening

Area of Science:

• Chemical Synthesis
• Organic Chemistry
• Biochemistry

Background:

• Aspartimide formation is an undesirable side reaction in solid-phase peptide synthesis.
• This reaction occurs under both acidic and basic conditions and is influenced by protecting groups, reagents, and peptide sequence.
• Hydrolysis of aspartimide-containing peptides during purification yields difficult-to-resolve alpha- and beta-aspartyl peptide mixtures.

Purpose of the Study:

• To elucidate optimal conditions for opening the aspartimide ring.
• To investigate the impact of various alcohols and bases on aspartimide ring opening.
• To apply optimized conditions to solid-phase peptide synthesis.

Main Methods:

• Systematic testing of different alcohol types (primary and secondary) and bases (diisopropylethylamine, collidine, 4-pyrrolidinopyridine, 1-methyl-2-pyrrolidone, piperidine, KCN).
• Evaluation of varying concentrations, temperatures, and reaction times.
• Application of identified optimal conditions to solid-phase peptide synthesis.

Main Results:

• Primary alcohols combined with diisopropylethylamine yielded the best aspartimide ring-opening results.
• Secondary alcohols required high temperatures to effectively open the aspartimide ring.
• The optimized conditions were successfully applied to solid-phase peptide synthesis, improving outcomes.

Conclusions:

• The study identified optimal conditions for aspartimide ring opening using primary alcohols and diisopropylethylamine.
• These findings provide a method to mitigate aspartimide-related purification challenges in peptide synthesis.
• The optimized conditions enhance the efficiency and success of solid-phase peptide synthesis.