Continuous-flow solid (gel)-phase peptide synthesis using unsupported ultrahigh-load polymers: Fmoc/t-butyl strategy

Area of Science:

• Organic Chemistry
• Biochemistry
• Chemical Engineering

Background:

• Solid-phase peptide synthesis (SPPS) is crucial for peptide production.
• Current SPPS methods face challenges with reagent removal and efficiency.
• Unsupported polymers offer potential advantages in SPPS.

Purpose of the Study:

• To extend continuous-flow SPPS using unsupported polymers.
• To incorporate N alpha-Fmoc protected amino acids into this system.
• To demonstrate the synthesis of challenging peptide sequences.

Main Methods:

• Utilized a continuous-flow reactor system with unsupported phenolic bead-form polymers (5 mmol g-1 loading).
• Employed a "layered displacement" technique for efficient reagent and washing solution removal under low pressure.
• Applied the N alpha-Fmoc protection strategy for amino acid coupling.

Main Results:

• Successfully adapted continuous-flow SPPS to N alpha-Fmoc protected amino acids.
• Demonstrated efficient synthesis of test peptides: [Leu5]-enkephalin and neurotensin.
• Achieved successful synthesis of the difficult acyl carrier protein decapeptide (65-74) sequence.

Conclusions:

• Continuous-flow SPPS with unsupported polymers is effective for N alpha-Fmoc protected amino acids.
• The "layered displacement" method enhances efficiency and simplifies reagent removal.
• This technique provides a robust platform for synthesizing complex peptides.