- Improved process for the preparation of nucleosidic phosphoramidites using a safer and cheaper activator
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A new, simplified commercial process for the preparation of nucleosidic phosphoramidites, key raw materials for the automated solid-supported synthesis of oligonucleotide-based drugs, was developed. Phosphitylation of a variety of protected nucleosidic derivatives (1-4) with a small excess of 2-cyanoethyl-N,N,N′,N′-tetraisopropyl phosphoramidite (5, bis-reagent) and pyridinium trifluoroacetate (Py·TFA) as the activator in an appropriate solvent at room temperature formed 75-96% of desired nucleosidic phosphoramidite products in less than 2 h. An efficient nonaqueous work-up has been developed to further streamline the isolation of moisture-sensitive P(III) nucleosidic compounds. The key finding is the use of Py·TFA, which is effective, inexpensive, stable, less acidic (pKa 5.2) than 1H-tetrazole, nontoxic, safe, and highly soluble in organic solvents. The reaction mechanism for phosphitylation with Py TFA as an activator has also been studied. An improved, robust, and versatile process for the preparation of nucleotide phosphoramidites under very concentrated reaction conditions was developed to support commercial manufacture of oligonucleotide-based drugs.
- Sanghvi, Yogesh S.,Guo, Zhiqiang,Pfundheller, Henrik M.,Converso, Antonella
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p. 175 - 181
(2013/09/07)
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- Some Steric Aspects of Synthesis of Oligoribonucleotides by Phosphoramidite Approach on Solid Support
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The influence of 2'-O-substituents (i.e. methyl, tetrahydropyranyl, tert-butyldimethylsilyl) on the chemical synthesis of oligoribonucleotides by phosphoramidite approach on solid support is described and compared with respective 2'-deoxynucleoside derivative.The observations on reactivity of these different 2'-O-protected derivatives at phosphatilation and condensation steps show their strong hindrance dependence.Some other aspects like reactivity of tetrahydropyranyl diastereoisomers, 3'- and 2'-O-phosphoramidites and some chemical properties of 2'-O-(tert-butyldimethylsilyl) protecting group are also presented.
- Kierzek, Ryszard,Rozek, Marek,Markiewicz, Wojciech T.
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p. 507 - 516
(2007/10/02)
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