Phosphorothioate anti-sense oligonucleotides: The kinetics and mechanism of the generation of the sulfurising agent from phenylacetyl disulfide (PADS)

James L. Scotson, Benjamin I. Andrews, Andrew P. Laws, Michael I. Page

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

The synthesis of phosphorothioate oligonucleotides is often accomplished in the pharmaceutical industry by the sulfurisation of the nucleotide-phosphite using phenylacetyl disulfide (PADS) which has an optimal combination of properties. This is best achieved by an initial 'ageing' of PADS for 48 h in acetonitrile with 3-picoline to generate polysulfides. The initial base-catalysed degradation of PADS occurs by an E1cB-type elimination to generate a ketene and acyldisulfide anion. Proton abstraction to reversibly generate a carbanion is demonstrated by H/D exchange, the rate of which is greatly increased by electron-withdrawing substituents in the aromatic ring of PADS. The ketene can be trapped intramolecularly by an o-allyl group. The disulfide anion generated subsequently attacks unreacted PADS on sulfur to give polysulfides, the active sulfurising agent. The rate of degradation of PADS is decreased by less basic substituted pyridines and is only first order in PADS indicating that the rate-limiting step is formation of the disulfide anion from the carbanion.

LanguageEnglish
Pages8301-8308
Number of pages8
JournalOrganic and Biomolecular Chemistry
Volume14
Issue number35
Early online date9 Aug 2016
DOIs
Publication statusPublished - 2016

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Phosphorothioate Oligonucleotides
oligonucleotides
Antisense Oligonucleotides
disulfides
Kinetics
kinetics
Anions
polysulfides
Disulfides
Picolines
anions
Phosphites
Pyridines
Degradation
Drug Industry
degradation
phenylacetyl disulfide
Sulfur
Protons
nucleotides

Cite this

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title = "Phosphorothioate anti-sense oligonucleotides: The kinetics and mechanism of the generation of the sulfurising agent from phenylacetyl disulfide (PADS)",
abstract = "The synthesis of phosphorothioate oligonucleotides is often accomplished in the pharmaceutical industry by the sulfurisation of the nucleotide-phosphite using phenylacetyl disulfide (PADS) which has an optimal combination of properties. This is best achieved by an initial 'ageing' of PADS for 48 h in acetonitrile with 3-picoline to generate polysulfides. The initial base-catalysed degradation of PADS occurs by an E1cB-type elimination to generate a ketene and acyldisulfide anion. Proton abstraction to reversibly generate a carbanion is demonstrated by H/D exchange, the rate of which is greatly increased by electron-withdrawing substituents in the aromatic ring of PADS. The ketene can be trapped intramolecularly by an o-allyl group. The disulfide anion generated subsequently attacks unreacted PADS on sulfur to give polysulfides, the active sulfurising agent. The rate of degradation of PADS is decreased by less basic substituted pyridines and is only first order in PADS indicating that the rate-limiting step is formation of the disulfide anion from the carbanion.",
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Phosphorothioate anti-sense oligonucleotides : The kinetics and mechanism of the generation of the sulfurising agent from phenylacetyl disulfide (PADS). / Scotson, James L.; Andrews, Benjamin I.; Laws, Andrew P.; Page, Michael I.

In: Organic and Biomolecular Chemistry, Vol. 14, No. 35, 2016, p. 8301-8308.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Phosphorothioate anti-sense oligonucleotides

T2 - Organic and Biomolecular Chemistry

AU - Scotson, James L.

AU - Andrews, Benjamin I.

AU - Laws, Andrew P.

AU - Page, Michael I.

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AB - The synthesis of phosphorothioate oligonucleotides is often accomplished in the pharmaceutical industry by the sulfurisation of the nucleotide-phosphite using phenylacetyl disulfide (PADS) which has an optimal combination of properties. This is best achieved by an initial 'ageing' of PADS for 48 h in acetonitrile with 3-picoline to generate polysulfides. The initial base-catalysed degradation of PADS occurs by an E1cB-type elimination to generate a ketene and acyldisulfide anion. Proton abstraction to reversibly generate a carbanion is demonstrated by H/D exchange, the rate of which is greatly increased by electron-withdrawing substituents in the aromatic ring of PADS. The ketene can be trapped intramolecularly by an o-allyl group. The disulfide anion generated subsequently attacks unreacted PADS on sulfur to give polysulfides, the active sulfurising agent. The rate of degradation of PADS is decreased by less basic substituted pyridines and is only first order in PADS indicating that the rate-limiting step is formation of the disulfide anion from the carbanion.

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