Phosphorothioate oligonucleotides

A supported sulfide source has been demonstrated by Zhang et al.16 to synthesize oligonucleotide phosphorothioates (entry 12). Aminodithiazole-thione attached to a methacrylate-ethyleneglycol copolymer is used to efficiently convert a nucleotide phosphite to a phosphorothioate. The product nucleotide possesses protecting groups suitable for solid-phase oligonucleotide synthesis and thus is a valuable building block for nucleic acid therapeutics. 

Zhang, R., Lu, Z., Zhao, H., Zhang, X., Diasio, R.B., Habus, I. et al. (1995b) In vivo stability, disposition, and metabolism of a hybrid oligonucleotide phosphorothioate in rats. Biochem. Pharmacol., 50, 545-556. 

The Synthesis of Stereodefined Oligonucleotide Phosphorothioates Possessing Modified Sugar Residues... 

Figure 19.3 Sulfurization reagents for the synthesis of oligonucleotide phosphorothioates bis(phenylacetyl) disulfide (13), tetraethylthiuram disulfide (14), dibenzoyl tetrasulfide (15), bis(0,0-diisopropoxyphosphinothioyl) disulfide (16),...

Phase transfer catalysis4 is a valuable tool in organic synthesis. The process is exemplified by the convenient synthesis of 2-chlorophenyl phosphoro-dichloridothioate. Using this phase transfer reaction, a number of dichloridothioates of substituted phenyl, benzyl, thiophenyl, and thiobenzyl alcohols are accessible. The phosphorodichloridothioate reacts with various coupling reagents to form activated species that are useful in the synthesis of oligonucleotide phosphorothioates via the phosphotriester approach as illustrated below.5 6... 

Karskela M, Virta P, Malincn M, Urtti A, Liamberg H (2008) Synthesis and cellular uptake of fluorescently labeled multivalent hyaluronan disacchaiide ctmjugates of oligonucleotide phosphorothioates. Bioctmjug Chem 19 2549-2558... 

Phosphorothioates. All three synthetic approaches appHcable to unmodified oligonucleotides can be adapted for synthesis of phosphorothioates (11) (33,46). If all of the phosphodiester linkages in an oligonucleotide are to be replaced with phosphorothioates, the ff-phosphonate method for coupling, followed by oxidation with Sg in carbon disulfide and triethylamine in the final step, is the most straightforward method. 

Other problems arise when modified oligonucleotides are synthesized. Oligonucleotides are most commonly synthesized today for pharmaceutical purposes in the form of phosphorothioates (PS), in which sulfurization of the phosphodiester bond has taken place (Figure 1). 

Bourque, A. J. and Cohen, A. S., Quantitative analysis of phosphorothioate oligonucleotides in biological fluids using fast anion-exchange chromatography, J. Chromatogr., 617, 43, 1993. 

A new antiviral agent, developed for treatment of CMV retinitis, can be administered by intravitreal injection. Formivirsen sodium is a phosphorothioate oligonucleotide that inhibits CMV replication through an antisense mechanism. It is formulated as a sterile and preservative-free solution and supplied in single-use vials (Vitravene ). The product is administered directly into the vitreous cavity posterior to the limbus through a 30-gauge needle. This procedure can be performed on an... 

Galbraith, W.M., Hobson, W.C., Giclas, PC., Schechter, P.J. and Agrawal, S. (1994). Complement activation and hemodynamic changes following intravenous administration of phosphorothioate oligonucleotides in the monkey. Antisense Res. Dev. 4 201-206. 

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