Total stepwise solid-phase synthesis of peptide-oligonucleotide conjugates using side-chain Boc/tBu protecting groups

Area of Science:

• Chemical Synthesis
• Bioconjugation Chemistry
• Oligonucleotide Chemistry

Background:

• Peptide-oligonucleotide conjugates are valuable tools in molecular biology and therapeutics.
• Traditional solid-phase synthesis methods face challenges with protecting group stability and side reactions.
• Developing robust and efficient synthesis strategies is crucial for advancing conjugate applications.

Purpose of the Study:

• To develop a practical and versatile solid-phase synthesis strategy for peptide-oligonucleotide conjugates.
• To utilize specific protecting groups that are compatible with oligonucleotide integrity.
• To overcome limitations of existing methods, such as acid-induced depurination and amino acid side reactions.

Main Methods:

• Employed Boc/tBu protecting groups for the side chains of specific amino acids (Trp, His, Arg, Asp, Glu).
• Utilized a mild deprotection condition in borate buffer at 90 °C.
• Performed total stepwise solid-phase synthesis of peptide-oligonucleotide conjugates.

Main Results:

• Successfully synthesized peptide-oligonucleotide conjugates using the developed strategy.
• Demonstrated that the chosen deprotection conditions prevent oligonucleotide depurination.
• Avoided the side reaction of deguanidination of the arginine residue.
• Confirmed the commercial availability of the required protected amino acids.

Conclusions:

• The developed Boc/tBu side-chain protection strategy offers a practical approach for synthesizing peptide-oligonucleotide conjugates.
• This method enhances the stability of the oligonucleotide component during synthesis.
• The strategy expands the scope and applicability of total stepwise solid-phase synthesis for creating complex biomolecular conjugates.