GalNAc Phosphoramidite Epimers With Racemization-Controlled Synthesis
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Solution Overview
Problem
The existing process for preparing GalNAc phosphoramidites leads to racemization at the designated chiral center during the coupling step, resulting in impure products.
Innovation Solution
A novel process involving the coupling of an epimerically pure compound with a GalNAc moiety to form a GalNAc amide, followed by removal of the hydroxyl protecting group and reaction with a phosphoroamidating agent to produce epimerically pure GalNAc phosphoramidite epimers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the reaction of GalNAc acid derivative with amino-protected amino acid is performed, then the GalNAc phosphoramidite can be prepared, but racemization occurs at the chiral center resulting in impure product
Solution Approach 1:
The invention applies preliminary action by performing the coupling reaction under carefully controlled conditions with specific additives (HOAt, HOBt, or DMAP) and at low temperatures (0-25°C) before racemization can occur. The reaction is designed to complete the coupling step quickly while maintaining chiral integrity, thus preventing racemization before it compromises product purity
Solution Approach 2:
The invention employs parameter changes by optimizing reaction conditions including temperature control (0-25°C), stoichiometry (1.05-1.5 equivalents of amino acid), and pH control (maintaining pH 6-8 with DIPEA). These parameter adjustments prevent racemization while ensuring complete coupling, thus resolving the contradiction between reaction efficiency and chiral purity
2Productivity
If the existing process is used to prepare GalNAc phosphoramidites, then the building block can be obtained, but a separate conjugation step is required reducing efficiency
Solution Approach 1:
The invention merges the GalNAc moiety directly into the phosphoramidite building block during the coupling reaction step. By incorporating the GalNAc-containing amino acid (Lys(Boc)-GalNAc or Lys(Fmoc)-GalNAc) directly into the phosphoramidite structure, the separate conjugation step is eliminated, thus combining multiple operations into one and improving synthesis efficiency
Solution Approach 2:
The invention creates a universal phosphoramidite building block that contains both the nucleoside attachment functionality and the GalNAc targeting moiety. This multi-functional building block can be directly used in oligonucleotide synthesis without requiring subsequent conjugation steps, thus simplifying the overall synthetic pathway and improving productivity
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 process ensures the production of epimerically pure GalNAc phosphoramidites, which can be directly used as building blocks in solid phase oligonucleotide synthesis without the need for a separate conjugation step, enhancing the purity and efficiency of the synthesis.
Implementation Method 1
reacting the free alcohol of the GalNAc acid amide of formula IV with a phosphoroamidating agent to form the GalNAc phosphoramidite epimer of the formula I
Data Source
AI summary
The invention comprises a process for the preparation of a GalNAc phosphoramidite epimer of the formula (I), wherein R1 is a hydroxy protecting group, n is an integer from 0 to 10 and m is an integer from 0 to 20, corresponding enantiomers and/ or optical isomers thereof and the use of the process for the preparation of GalNAc-cluster oligonucleotide conjugates.