Oligonucleoside phosphorothioates, syntheses

Deoxyribonucleotides, deoxyribonucleotide phosphorothioates, modified DNA, and analogs have wide applications in molecular biology, antisense applications, antigene therapy, etc. Three methods are available for the synthesis of oligonucleoside phosphorothioates phosphoramidite, H-phosphonate, and phospho-... 

In the area of modified intemucleosidic links, the use of the selenium-containing system 186 in the synthesis of oligonucleoside phosphorothioates has been prefmed to the earlier sulfur analogue since the P-Se bond is more labile in reaction with the 5 -OH group of the other... 

As a final addendum to the commentary in Section 3., it is worthwhile to discuss briefly two subjects of continual interest in the area of potential pharmaceutical applications of oligonucleoside phosphorothioates scale-up vis-a-vis solid-phase or solution synthesis and stereochemistry. ... 

However, conversion of the dinucleoside //-phosphonate diester 10 to the phosphorothioate analogue 11 effected by a 0.02 M solution of 2 in 2% aqueous pyridine is relatively slow it reportedly takes 3 h for a complete reaction. While a solution of 2 in 2% aqueous acetonitrile containing triethylamine can completely transform 10 into 11 within 30 s, the use of this sulfurization mixture is incompatible with automated solid-phase oligonucleotide synthesis given the rapid formation of a yellow precipitate caused by triethylamine. In the absence of triethylamine, 10 is not sulfurized under these conditions. Nonetheless, 10 is completely converted to 11 within 20 min when a 0.02 M solution of 1 in 2% aqueous pyridine is used for the sulfurization reaction. Thus, 3i/-l,2-benzodithiol-3-one in aqueous pyridine is compatible with automated solid-phase synthesis of both DNA and RNA oligonucleoside phosphorodithioates or phosphorothioates from appropriate //-phosphonate derivatives. ... 

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