Fluorine-Substituted Ether Protecting Group for RNA Synthesis
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Solution Overview
Problem
Current protective groups for the 2'-hydroxyl group in ribonucleosides and ribonucleotides, such as TBDMS and CEE, face issues like steric hindrance, instability, and inefficient removal, leading to reduced yield and increased manufacturing costs in oligoribonucleic acid synthesis.
Innovation Solution
A protective group represented by the general formula -CH2-O-CH2-CH2-WG1, where WG1 is an electron withdrawing group, is introduced, which is stable under reaction conditions, has minimal steric hindrance, and can be efficiently removed under mild fluoride ion treatment or strongly basic conditions with a nucleophile scavenger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If TBDMS protective group is used for 2'-hydroxyl group, then the protective group can be removed by fluoride ions under neutral conditions, but the group translocates to 3'-hydroxyl group during phosphoroamidation and causes steric hindrance reducing condensation reaction efficiency
Solution Approach 1:
The patent modifies the protective group structure by changing the alkyl chain length and fluorine substitution pattern (from TBDMS to TFEOM), altering its chemical properties to prevent translocation while maintaining fluoride ion removability. This structural parameter change resolves the contradiction between ease of removal and condensation reaction efficiency.
2Productivity
If CEE protective group is used for 2'-hydroxyl group, then efficient preparation of oligoribonucleic acids is achieved, but the group is unstable to acids and generates acrylonitrile causing side reactions with nucleobase moieties
Solution Approach 1:
The patent employs a protective group (TFEOM) that is designed to be removed completely under mild fluoride ion conditions without generating persistent harmful byproducts. The group serves its protective function temporarily and is then eliminated cleanly, avoiding the acrylonitrile side reactions associated with CEE groups.
3Ease of operation
If CEM protective group is used for 2'-hydroxyl group, then the group has little steric hindrance and can be removed by fluoride ions, but removal efficiency is not satisfactory and strict control of water content in solvent is required
Solution Approach 1:
The patent modifies the protective group structure by extending the ether chain and adding fluorine substituents (TFEOM vs CEM), which enhances the group's stability toward fluoride ions while maintaining low steric hindrance. This structural modification allows removal under milder, more practical conditions without strict water content control.
4Stability of the object's composition
If protective group is stable under reaction conditions, then sufficient stability is secured for long chain synthesis, but removal efficiency may be reduced
Solution Approach 1:
The patent introduces a fluorine atom as an intermediary that selectively interacts with the protective group under mild conditions. The TFEOM group remains stable during synthesis but responds specifically to fluoride ion treatment for removal, achieving both stability during reaction and efficient removal when needed.
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
This group allows for stable and efficient synthesis of oligoribonucleic acids with improved yield and reduced manufacturing costs, as it can be easily deprotected without stringent solvent moisture control, facilitating multiple step deprotection processes.
Implementation Method 1
the group was very efficiently and quickly removable by treatment with fluoride ions under mild conditions
Implementation Method 2
WG1 in the formula represents an electron withdrawing group
Data Source
AI summary
A protective group represented by the following general formula (I) (the oxygen atom attached with * represents oxygen atom of 2'-hydroxyl group of a ribonucleoside, a ribonucleotide or a derivative thereof, R1 and R2 both represent hydrogen atom, or represent a halogen atom, a C1-6 alkyl group, or a C1-6 halo-substituted alkyl group; R3 and R4 represent hydrogen atom, a halogen atom, a C1-6 alkyl group, or a C1-6 halo-substituted alkyl group; and R5 and R6 represent a halogen atom, a C1-6 halo-substituted alkyl group, cyano group, nitro group, or the like), which is stable under the reaction conditions of the nucleic acid synthetic cycles and has little steric hindrance, and can be removed under mild conditions using fluoride ions as a base.