Improved Procedure for the Detritylation of DMT-Oligonucleotides: Use of Dowex®

Solution-phase synthesis of di- and trinucleotides using polymer-supported reagents

A solution-phase phosphoramidite synthesis of short oligonucleotides using solid-supported reagents is described. Polyvinyl pyridinium tosylate is employed as the activator in the coupling step between nucleoside-3'-O-phosphoramidites and 5'-OH nucleosides. The resulting dinucleotide phosphite triesters are oxidized or sulfurized with polymer-bound periodate or tetrathionate to phosphotriesters or thiono phosphotriesters, respectively. Removal of the 3'-O-levulinyl protection is accomplished with a polymer-supported hydrazine. In this approach, the excess reagents are removed by filtration, avoiding complicated purifications. All the polymer-bound reagents used in this method result from salt bridge interactions with the polymers. Consequently, the resins are regenerable.

High-yield solution-phase synthesis of di- and trinucleotide blocks assisted by polymer-supported reagents

A new solution-phase phosphoramidite approach is reported for oligonucleotide synthesis employing recyclable solid-supported reagents. It uses polyvinyl pyridinium tosylate as the activator of a nucleoside-3'-O-phosphoramidite in the coupling step with a 5'-OH nucleoside or dinucleotide. The resulting phosphite triester was either sulfurized or oxidized using polystyrene-bound trimethylammonium tetrathionate or periodiate. This method avoids complicated purification steps, as excess reagents are easily removed by filtration. [reaction: see text]

Protection of 5'-hydroxy functions of nucleosides

The 5-hydroxy group is the primary hydroxy group of nucleosides. It is mandatory to protect 5-hydroxyls in all methods of oligonucleotide synthesis that require nucleoside synthons. This unit discusses a wide variety of acid-labile and base-labile protecting groups, as well as enzymatic methods for 5-protection and deprotection.