A new method for introducing amidate linkages in oligonucleotides using phosphoramidite chemistry

Area of Science:

• Chemical Synthesis
• Oligonucleotide Chemistry
• Biochemistry

Background:

• Phosphotriester linkages are common in oligonucleotide synthesis.
• Modifications to oligonucleotide linkages can alter their properties and applications.
• Developing efficient methods for linkage conversion is crucial for oligonucleotide research.

Purpose of the Study:

• To develop a method for converting cyanoethyl-protected phosphotriester linkages to phosphoramidate linkages.
• To utilize standard phosphoramidite chemistry for this conversion.
• To enable the synthesis of modified oligonucleotides with phosphoramidate backbones.

Main Methods:

• Oligonucleotides with cyanoethyl-protected phosphotriester linkages were synthesized on solid support.
• The cyanoethyl protecting group was removed using piperidine.
• The resulting phosphodiester was activated with p-tosyl chloride.
• An amine nucleophile was used to displace the tosyl group, forming a phosphoramidate linkage.

Main Results:

• Successful conversion of phosphotriester to phosphoramidate linkages was achieved.
• The method is compatible with standard solid-phase oligonucleotide synthesis.
• The process utilizes readily available reagents like piperidine and p-tosyl chloride.

Conclusions:

• A novel and efficient method for synthesizing phosphoramidate linkages in oligonucleotides has been established.
• This method offers a valuable tool for creating modified oligonucleotides with potential therapeutic or diagnostic applications.
• The described chemistry provides a pathway to explore the biological impact of phosphoramidate backbones in nucleic acids.