Phosphorus Protecting Groups for Mild Base Oligonucleotide Deprotection
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Solution Overview
Problem
The existing methods for chemical synthesis of oligonucleotides, particularly RNA, face challenges with the use of strong bases for deprotection, which are not suitable for mildly basic conditions and can inhibit the reactivity of phosphoramidite reagents due to electron-withdrawing groups and crowding around the phosphorus center.
Innovation Solution
Development of novel phosphorus protecting groups that are labile under mildly basic conditions with α-effect nucleophiles, allowing for efficient deprotection without the need for strong bases and minimizing reactivity inhibition, along with the use of peroxyanion solutions at pH below 11.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If strong bases (ammonia, methyl amine) are used for deprotection of phosphorus protecting groups, then complete removal of protecting groups is achieved, but the reactivity of phosphoramidite reagents is inhibited due to electron-withdrawing groups and crowding around the phosphorus center
Solution Approach 1:
The patent changes the chemical parameters of the deprotection system by introducing peroxyanion-based reagents (such as peracetic acid, performic acid, or in situ generated peroxyanions) that operate at mildly basic pH (below 11), replacing the traditional strong base system. This parameter change allows deprotection to proceed without the severe reactivity inhibition caused by strong bases, thereby resolving the contradiction between complete deprotection and maintaining phosphoramidite reactivity
Solution Approach 2:
The patent employs peroxyanion intermediates as mediators in the deprotection process. These intermediates (RCO3- ions generated from peracids or in situ from hydrogen peroxide and carboxylic acids) serve as the active deprotecting species that can remove phosphorus protecting groups under mild conditions. The intermediary approach enables effective deprotection while avoiding the harsh conditions that inhibit phosphoramidite reactivity
2Ease of manufacture
If standard protecting groups optimized for strong base removal are used, then deprotection can be achieved under conventional conditions, but they require strong bases that are not suitable for mildly basic conditions and can inhibit reactivity
Solution Approach 1:
The patent modifies the deprotection parameters by using peroxyanion-based chemistry at pH below 11, creating a new operational regime that is compatible with RNA synthesis. This parameter change makes the process adaptable to mild conditions while maintaining ease of manufacture through the use of commercially available peracids or in situ generation methods
Solution Approach 2:
The patent develops protecting groups with structure (V) that are universally applicable to phosphorus groups in oligonucleotide synthesis and can be removed under the new mild peroxyanion-based conditions. This multi-functional protecting group design provides both ease of manufacture and adaptability to mild conditions, resolving the contradiction between conventional deprotection ease and compatibility with mild basic conditions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables effective deprotection of phosphorus protecting groups in oligonucleotide synthesis, improving the efficiency and compatibility with RNA synthesis by maintaining reactivity and stability under mild conditions.
Implementation Method 1
This method utilizes the strong nucleophilicity of peroxyanions at mildly basic pH
Implementation Method 2
contacting a polynucleotide with a solution comprising an α-effect nucleophile, wherein the polynucleotide comprises a phosphorus group and a phosphorus protecting group bound to the phosphorus group; contacting resulting in cleavage of the phosphorus protecting group from the phosphorus group
Data Source
AI summary
Compounds having a phosphorus group structure of:wherein:R is alkyl, modified lower alkyl; andRi and Ri are each independently H, alkyl, modified alkyl, or aryl; are provided. Also provided are polynucleotide compositions that include these compounds and methods of using the compounds in synthesis of the same.