Recent Progress in Oligoribonucleotide Synthesis

Nucleobase Protection of Deoxyribo- and Ribonucleosides

Oligonucleotides carrying a variety of chemical modifications including conjugates are finding increasing applications in therapeutics, diagnostics, functional genomics, proteomics, and as research tools in chemical and molecular biology. The successful synthesis of oligonucleotides primarily depends on the use of appropriately protected nucleoside building blocks including the exocyclic amino groups of the nucleobases, the hydroxyl groups at the 2'-, 3'-, and 5'-positions of the sugar moieties, and the internucleotide phospho-linkage. This unit is a thoroughly revised update of the previously published version and describes the recent development of various protecting groups that facilitate reliable oligonucleotide synthesis. In addition, various protecting groups for the imide/lactam function of thymine/uracil and guanine, respectively, are described to prevent irreversible nucleobase modifications that may occur in the presence of reagents used in oligonucleotide synthesis. © 2017 by John Wiley & Sons, Inc.

Strategies for oligoribonucleotide synthesis according to the phosphoramidite method

Advances in oligoribonucleotide synthesis have lagged behind those in oligodeoxyribonucleotide synthesis because of the difficulty in identifying orthogonal protecting groups for the 2'- and 5'-hydroxyls. Adaptation of the phosphoramidite method for DNA synthesis to RNA synthesis has greatly improved our understanding of RNA. It allows site-specific introduction of modified nucleosides to any position in an RNA molecule, as well as introduction of variations at multiple sites in the molecule. This overview discusses issues that are relevant to RNA synthesis by the phosphoramidite approach, including supports used, activation of the ribonucleoside phosphoramidites, and protection of the nucleobase, phosphate, and 2'- and 5'-hydroxyls.

Nucleobase protection of deoxyribo- and ribonucleosides

Protecting groups for the imide/lactam function of thymine/uracil and guanine, respectively, prevent irreversible nucleobase modifications that may occur in the presence of alkylating or condensing reagents that are commonly used in nucleoside protection and oligonucleotide synthesis. This unit reviews these protecting groups, and also identifies protecting groups for the exocyclic amino function of cytosine, adenine, and guanine. The unit also explores recent trends in nucleobase protection that permit reliable oligonucleotide synthesis and removal of N-protecting groups under very mild conditions.