Fmoc-Protected Morpholino Monomers for Stable PMO Synthesis
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Solution Overview
Problem
Current methods for synthesizing phosphorodiamidate morpholino oligonucleotides (PMOs) are inefficient due to unstable Trityl-protected chlorophosphoramidate monomers, which decompose quickly in the presence of organic or inorganic bases, requiring lengthy synthesis times and complex deblocking processes, and lack stability in solution, making it difficult to produce longer oligomers like 25-mers efficiently.
Innovation Solution
Development of Fmoc-protected chlorophosphoramidate and H-phosphonate monomers that are stable in common organic solvents, allowing for efficient chain elongation via peptide or DNA synthesizers, using activators like ETT instead of LiBr for improved coupling efficiency and higher monomer concentrations, and employing piperidine-mediated deblocking for easier Fmoc group removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Trityl-protected chlorophosphoramidate monomers are used for PMO synthesis, then the synthesis can proceed with existing methods, but the monomers decompose quickly in the presence of organic or inorganic bases, requiring lengthy synthesis times and complex deblocking processes
Solution Approach 1:
The patent changes the protecting group from Trityl to Fmoc, which fundamentally alters the chemical stability parameters of the monomer. Fmoc-protected monomers are stable in the presence of bases used during synthesis, eliminating the decomposition issue that plagues Trityl-protected monomers and enabling longer synthesis times without loss of monomer integrity
Solution Approach 2:
The patent extracts and removes the problematic Trityl protecting group system entirely, replacing it with Fmoc protection. This eliminates the need for complex deblocking processes involving prolonged exposure to acidic conditions and multiple washing steps, thereby reducing overall synthesis time and complexity
2Ease of manufacture
If Trityl-protected monomers are used, then existing synthesis protocols can be maintained, but the monomers lack stability in solution, making it difficult to produce longer oligomers like 25-mers efficiently
Solution Approach 1:
The patent changes the protecting group chemistry from Trityl to Fmoc, which fundamentally improves solution stability. Fmoc-protected monomers remain stable in solution for extended periods, enabling the efficient production of longer oligomers (25-mers) without premature decomposition that occurs with Trityl-protected monomers
3Ease of manufacture
If LiBr is used as coupling reagent, then the synthesis can proceed with traditional reagents, but the coupling efficiency is lower and requires more time per coupling step
Solution Approach 1:
The patent changes the coupling reagent from LiBr to ETT (5-ethylthio-1H-tetrazole), which dramatically improves coupling efficiency. This reagent change enables faster coupling reactions with higher yields, reducing the time required per coupling step while maintaining ease of manufacture through simple procedural modifications
4Reliability
If complex deblocking processes are used for Trityl removal, then complete deblocking can be achieved, but the process becomes lengthy and reduces overall synthesis efficiency
Solution Approach 1:
The patent extracts and removes the complex Trityl deblocking process entirely by adopting Fmoc protection. Fmoc removal uses simple base treatment (20% piperidine in DMF) that is both complete and rapid, eliminating the lengthy multi-step acidic deblocking procedures required for Trityl groups and thereby increasing overall synthesis throughput
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
The Fmoc-protected monomers enable faster and more stable synthesis of PMOs, achieving high yields and improved coupling efficiency, allowing for the production of longer oligomers without decomposition, and can be used in both peptide and DNA synthesizers, overcoming the limitations of Trityl-protected monomers.
Implementation Method 1
employing piperidine-mediated deblocking for easier Fmoc group removal
Implementation Method 2
using activators like ETT instead of LiBr for improved coupling efficiency
Data Source
AI summary
Present invention relates to stable Fmoc protected Morpholino monomers and corresponding oligonucleotides (PMO) and efficient synthesis of the same involving chlorophosphoramidate and H-Phosphonate chemistry. Successful syntheses of the oligonucleotide with higher yield and lesser time have been accomplished employing solid phase synthesis and easy deprotection of Fmoc group with Piperidine.