Oligonucleotide Deprotection Using Low-Concentration DBU
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Solution Overview
Problem
Current methods for deprotecting β-cyanoethyl protective groups in oligonucleotide synthesis, such as those described in US patents 6,858,715 and 7,199,236, face challenges in avoiding the formation of cyanoethyl adducts to nucleobases, particularly thymidine, and require specific pKa ranges for effective deprotection.
Innovation Solution
A process using 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) in a halogenated or cyanoalkyl solvent, with concentrations below 0.5 M, allows for the efficient removal of β-cyanoethyl protective groups from oligonucleotides attached to a solid support, minimizing side-reactions and adduct formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a strong base with pKa greater than 11.5 is used for deprotection, then deprotection efficiency is improved, but formation of cyanoethyl adducts to nucleobases increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the concentration of strong base (DBU) in the deprotection solution. By using low concentrations (0.01-0.5 M, preferably 0.03-0.1 M) of DBU with pKa greater than 11.5 in halogenated solvents, the patent achieves effective deprotection while minimizing cyanoethyl adduct formation. This concentration optimization resolves the contradiction between deprotection efficiency and side reaction suppression.
2Reliability
If conventional deprotection methods are used, then deprotection can be achieved, but selectivity and yield are reduced due to side-reactions
Solution Approach 1:
The patent improves selectivity by changing the chemical parameters of the deprotection system. It uses DBU in halogenated solvents at optimized concentrations (0.01-0.5 M), which provides complete deprotection while minimizing side reactions. The specific combination of base strength, concentration, and solvent type creates selective deprotection conditions that preserve nucleobase integrity.
Solution Approach 2:
The patent uses halogenated solvents as intermediaries to facilitate the deprotection reaction. These solvents (dichloromethane, chloroform, 1,2-dichloroethane) serve as media that enable effective deprotection by DBU while reducing direct interaction between the base and nucleobases, thereby preventing cyanoethyl adduct formation and improving overall selectivity.
3Speed
If high concentration of DBU is used, then deprotection speed increases, but side-reactions and adduct formation increase
Solution Approach 1:
The patent optimizes the DBU concentration parameter to balance reaction speed and side reaction suppression. By using low concentrations (0.01-0.5 M, preferably 0.03-0.1 M) rather than high concentrations, the patent achieves sufficient deprotection rates while minimizing cyanoethyl adduct formation. The halogenated solvents enhance the effectiveness of these low concentrations, maintaining adequate reaction speed.
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 high selectivity and yield in deprotecting β-cyanoethyl protected oligonucleotides while avoiding undesirable side-reactions, even at lower DBU concentrations and shorter reaction times, maintaining the integrity of the oligonucleotides attached to the solid support.
Implementation Method 1
removing comprises contacting the protected oligonucleotide in a column having inlet and outlet openings with from 2 to 60 column volumes of a solution of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)
Data Source
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AI summary
A process for manufacturing an oligonucleotide which comprises removing ß-eliminating phosphorus-protecting groups, in particular ß-cyanoethyl protective groups from a protected oligonucleotide, wherein said removing comprises contacting the protected oligonucleotide with an amine solution in a solvent which preferably does not consist of pyridine, wherein the conjugate acid of the amine has preferably a pKa of greater than 11.5, and wherein the concentration of the amine in the solution is less than 0.5 mole/liters.