2'-Hydroxyl Ribonucleoside Derivative Synthesis via Michael Reaction
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Solution Overview
Problem
Conventional methods for synthesizing RNA with modified 2'-hydroxyl groups face challenges such as the production of positional isomers, instability of protecting groups, and limited incorporation of ester skeletons, making it difficult to incorporate simpler ester skeletons like methyl ester or ethyl ester into the 2'-hydroxyl group of ribonucleosides.
Innovation Solution
A Michael reaction using an α, β-unsaturated ester, specifically acrylic acid ester, is employed to incorporate an alkoxycarbonylethyl group into the 2'-hydroxyl group of ribonucleosides under mild reaction conditions, allowing for the incorporation of various ester functional groups and enabling the formation of ribonucleoside derivatives with improved stability and reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods using NaH and alkyl halide are used to synthesize 2'-modified ribonucleosides, then the 2'-hydroxyl group can be alkylated, but positional isomers (3'-modified products) are produced in large amounts making separation difficult
Solution Approach 1:
The 3'- and 5'-hydroxyl groups are protected in advance with a protecting group before the alkylation reaction. This preliminary protection action prevents these groups from reacting with the alkyl halide, ensuring that only the 2'-hydroxyl group is modified and eliminating the formation of positional isomer by-products.
Solution Approach 2:
A protecting group acts as an intermediary that temporarily blocks the 3'- and 5'-hydroxyl groups during the alkylation reaction. This intermediary allows the reaction to proceed selectively at the 2'-position while preventing unwanted side reactions at other positions, and the protecting group can be removed afterward to restore the original functionality.
2Ease of manufacture
If protecting groups such as TIPS or DBS are used to protect 3'- and 5'-hydroxyl groups, then simultaneous protection is achieved, but these protecting groups are unstable to reagents such as NaH and BEMP producing by-products
Solution Approach 1:
The patent changes the chemical parameters of the protecting group from conventional options (TIPS, DBS) to a novel protecting group that exhibits enhanced stability under basic conditions. This parameter change in the chemical structure and properties of the protecting group allows it to withstand strong bases like NaH and BEMP without decomposition, eliminating by-product formation while maintaining the ability to protect multiple hydroxyl groups simultaneously.
3Manufacturing precision
If strict basic conditions are employed in synthesis methods, then 2'-alkylation can be achieved, but it is impossible to incorporate functional groups such as methyl ester or ethyl ester into the alkyl halide derivative
Solution Approach 1:
The patent changes the reaction condition parameters from strict basic conditions to milder conditions. This parameter change allows ester functional groups (methyl ester, ethyl ester) to be incorporated into the alkyl halide derivative without degradation or unwanted side reactions, while still achieving effective 2'-alkylation of the ribonucleoside.
4Reliability
If only tert-butyl ester is incorporated as ester skeleton to maintain stability, then stability is maintained, but the choice of ester skeleton is limited
Solution Approach 1:
The patent changes the stability parameter by introducing a novel protecting group that provides enhanced stability under basic conditions. This parameter change enables the use of various ester skeletons (methyl ester, ethyl ester, and others) beyond just tert-butyl ester, as the new protecting group stabilizes the system against base-catalyzed degradation, thus expanding the versatility of ester group choices.
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 approach enables the incorporation of ester functional groups, providing new materials for antisense and RNAi methods, and allows for the use of amide groups and fluorescent labels, enhancing the stability and utility of RNA synthesis.
Implementation Method 1
a Michael reaction using an acrylic acid ester, which is α, β-unsaturated ester, under very mild reaction conditions
Data Source
AI summary
Provided is a ribonucleoside derivative represented by General Formula (I): (wherein R1 represents a hydrogen atom or the like, R2 represents a hydrogen atom or the like, R3 represents a methyl group or the like, and B represents a nucleic acid base residue optionally having a protecting group or a modifying group). An RNA containing this ribonucleoside derivative shows excellent hybridization ability and resistance to nuclease.