Ribonucleotide Oligomer Synthesis Using Dimer Trimer Synthons
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Solution Overview
Problem
The synthesis of RNA oligomers is hindered by steric hindrance of protecting groups, leading to low coupling efficiency and long synthesis times, resulting in low production yield and purity issues, particularly for ribonucleotide oligomers and siRNAs.
Innovation Solution
Using a ribonucleotide dimer or trimer as the first nucleotide synthon bound to solid supports, followed by sequential coupling of monomers, significantly reduces impurity formation and facilitates high-purity production by minimizing the formation of shorter sequence impurities during the synthesis process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional monomeric phosphoramidite synthesis is used, then the synthesis process is simple, but coupling efficiency is low and synthesis time is long due to steric hindrance of protecting groups
Solution Approach 1:
The patent divides the nucleotide building block into segmented units by using protected nucleosides with strategically placed protecting groups that can be selectively removed and reprotected. This segmentation allows for stepwise assembly of oligonucleotides while maintaining coupling efficiency despite the presence of protecting groups on adjacent nucleotides.
Solution Approach 2:
The patent applies preliminary action by pre-protecting specific hydroxyl groups (2'-OH and 3'-OH) before coupling reactions. The 2'-OH is protected with groups like TBDMS or TOM, and the 3'-OH is protected with CEM or CNEE groups. These preliminary protective measures prevent unwanted side reactions and enable efficient coupling by directing the reaction to the correct nucleophilic site.
2Ease of manufacture
If conventional monomeric phosphoramidite synthesis is used, then the methodology is straightforward, but production yield is low due to incomplete coupling
Solution Approach 1:
The patent incorporates feedback mechanisms through rigorous monitoring of coupling reactions using UV absorbance measurements and trityl cation release quantification. This real-time feedback allows optimization of coupling conditions and identification of incomplete couplings, enabling corrective actions to maximize production yield.
Solution Approach 2:
The patent systematically varies critical parameters including coupling time, activator concentration, and temperature to optimize coupling efficiency. By changing these parameters based on feedback from intermediate analysis, the methodology achieves higher production yields while maintaining operational simplicity.
3Ease of manufacture
If conventional synthesis methods are used, then the process is conventional and well-established, but purity is low due to formation of shorter sequence impurities
Solution Approach 1:
The patent applies preliminary anti-action by using protecting groups that prevent the formation of shorter sequence impurities from the outset. The 2'-OH protection prevents 2'-O-alkylation side reactions, and the selective 3'-OH protection prevents premature phosphite triester formation. This preliminary protective strategy prevents impurity formation rather than requiring extensive post-synthesis purification.
Solution Approach 2:
The patent converts the potential harm of having multiple protected groups into a benefit by using the protecting groups themselves as directing elements for selective coupling. The protecting groups that would normally be seen as obstacles are instead used to direct the coupling reaction to the correct nucleophilic site, thereby improving both purity and coupling efficiency.
4Ease of manufacture
If conventional synthesis methods are used, then the methodology is standard, but synthesis time is long due to low coupling efficiency
Solution Approach 1:
The patent achieves continuity of useful action by optimizing the synthesis cycle to minimize idle time between coupling steps. The protecting group strategy enables continuous coupling reactions without requiring intermediate deprotection steps, as the protecting groups remain intact throughout the synthesis process and are removed only in the final deprotection step. This continuous action significantly reduces total synthesis time while maintaining methodological standardization.
Data Source
AI summary
The present invention provides a method for preparing nucleotide oligomers, including (a) coupling a nucleotide dimer or nucleotide trimer to a nucleoside attached to solid supports or to universal solid supports as a starting material; (b) sequentially coupling nucleotide monomers to the resulting structures of Step (a) to prepare a nucleotide oligomer; and (c) removing the nucleotide oligomers from the solid supports. The method of the present invention provides nucleotide oligomers having 15-20% higher purity than the conventional art. The present invention enables the efficient and inexpensive synthesis of nucleotide oligomers with high purity within a shorter period of time.