Pneumococcus Serotype 5 Polysaccharide Reductive Amination
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Solution Overview
Problem
Conventional reductive amination methods for pneumococcus type 5 capsular polysaccharide modification result in unintended chemical structure changes, leading to reduced immunogenicity due to the formation of compound X, which is harmful to the polysaccharide's immunogenic properties.
Innovation Solution
Modifying the reductive amination process by reducing ketone functions using a strong reducing agent like NaBH4 before fragmentation, and then subjecting the polysaccharide to reductive amination under optimized conditions to prevent the formation of compound X, ensuring amination primarily on the terminal aldehyde group.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional reductive amination methods are used to modify pneumococcus type 5 capsular polysaccharide, then amination of the polysaccharide is achieved, but unintended chemical structure changes occur leading to reduced immunogenicity
Solution Approach 1:
The patent applies preliminary action by selectively reducing ketone functions to hydroxyl groups before performing the reductive amination reaction. This preliminary reduction prevents the formation of compound X during subsequent amination, thereby maintaining immunogenicity while achieving the desired amination modification
Solution Approach 2:
The patent changes the chemical state of the polysaccharide by selectively reducing ketone groups to hydroxyl groups, altering the reactivity parameters of the molecule. This parameter change ensures that only terminal aldehyde groups undergo amination, preventing unwanted side reactions that would compromise immunogenicity
2Productivity
If reductive amination is performed without preliminary reduction of ketone functions, then amination proceeds, but compound X forms which is harmful to immunogenicity
Solution Approach 1:
The patent applies preliminary anti-action by reducing ketone functions before amination to prevent the formation of harmful compound X. This counter-action eliminates the source of the harmful byproduct while preserving the desired amination reaction and maintaining immunogenicity
Solution Approach 2:
The patent converts the potentially harmful ketone groups into beneficial hydroxyl groups through selective reduction. This transformation eliminates the source of compound X formation while the resulting hydroxyl groups do not interfere with the desired amination process, effectively turning a harmful feature into a benign one
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 modified process significantly reduces the formation of compound X, maintaining the polysaccharide's immunogenicity by ensuring amination primarily on the terminal aldehyde group, resulting in a higher percentage of aminated polysaccharide units with preserved immunogenicity.
Implementation Method 1
reacting the polysaccharide with an agent capable of reducing a ketone function
Implementation Method 2
a reductive amination reaction takes place in two steps. In a first step, an intermediate compound, called Schiff base, of formula R—CH═NH+—R′, forms resulting from the interaction between an aldehyde group of a first molecule (R—CHO) and a primary amine group (R′—NH2) of a second molecule. The Schiff base is then reduced in a second step in the form of an amino compound R—CH2—NH—R′
Data Source
AI summary
The invention relates to conjugates derived from the reductive amination of the pneumococcus serotype 5capsular polysaccharide. The conditions for reductive amination differ from conventional conditions in that they make it possible to avoid the appearance of an undesirable compound which harms the immunogenicity of the conjugates. In carbon NMR spectrum, this undesirable compound is characterized by a resonance signal between 13 and 14 ppm. The aminated polysaccharides used to produce the conjugates therefore have a carbon NMR spectrum lacking a resonance signal between 13 and 14 ppm. The invention offers two conditions for reductive amination. According to a first method, the reductive amination is carried out at a slightly acidic pH (4-6.5) for at the very most 4 hours. According to a second method, the polysaccharide is first of all reduced, then fragmented and, finally, subjected to a reductive amination per se, under conditions which may or may not be conventional. Depending on the method used, the structure of the aminated polysaccharide may vary (conversion or not of the Sug residue of the repeating unit to N-acetylated quinovosamine and to N-acetylated fucosamine); however, these variations, as recorded in carbon NMR spectrometry, have no effect on the immunogenicity.