Postsynthetic on column RNA labeling via Stille coupling.

Area of Science:

• Organic Chemistry
• Nucleic Acid Chemistry
• Biotechnology

Background:

• The Stille coupling reaction is a powerful tool for carbon-carbon bond formation, known for its functional group tolerance and mild reaction conditions.
• Automated solid-phase synthesis is a standard technique for producing RNA oligonucleotides.
• Post-synthetic modification of RNA allows for the introduction of diverse functionalities.

Purpose of the Study:

• To develop an on-column RNA modification strategy using Stille cross-coupling.
• To enable site-specific functionalization of RNA while it remains attached to the solid support.
• To synthesize fluorescently labeled RNA oligonucleotides.

Main Methods:

• Incorporation of iodo-substituted nucleotide precursors into RNA during automated solid-phase synthesis using TBDMS, TC, and ACE protecting groups.
• On-column Stille cross-coupling reactions between the immobilized RNA and organostannanes.
• Optimization of coupling conditions including catalyst/ligand systems, temperature, reaction time, and heating methods (conventional vs. microwave).
• Deprotection and cleavage from the solid support to yield the final labeled RNA oligonucleotides.

Main Results:

• Successful demonstration of on-column Stille cross-coupling for RNA modification.
• Optimization of reaction parameters leading to efficient coupling.
• Synthesis of site-specifically labeled 5-mer and 12-mer RNA oligonucleotides.
• Generation of fluorescently functionalized RNA using various organostannanes (vinyl, furanyl, thiophene, benzothiophene).

Conclusions:

• The developed on-column Stille coupling strategy provides a versatile and efficient method for site-specific RNA modification.
• This approach integrates seamlessly with standard automated solid-phase RNA synthesis.
• The method allows for the introduction of diverse functional groups, including fluorescent labels, onto RNA oligonucleotides.