Protecting Groups for the Synthesis of Polynucleotides

Naturally occurring nucleic acids consist of nucleosides joined by phosphoric diester linkages between the 3 -hydroxyl group of one 

Protection of the 3 -hydroxyl group in stepwise synthesis of oligo(deoxyribonucleotides) has usually involved the acetyl or, sometimes, the isobutyryl group, with removal after each condensation by brief treatment with base (so as not to remove alkali-labile, N-acyl pro- 

Direct 2 - or 3 -0-benzylation of nucleosides has been reported,71,95,96 but removal of the benzyl group by catalytic hydrogen-olysis is not straightforward. The deprotection of methyl-substituted-benzyl ethers of nucleosides has been effected by treatment with acid. An improvement here has been the use of the photosensitive o-nitro- 

A useful approach that has emerged from study of protecting groups for the cis-diol groupings of ribonucleoside involved the subtle use of 0-2 (3 )-substituted nucleoside 5 -diphosphates in single-addition 

In the Werstiuk-Neilson approach to the synthesis of oligonucleotides by the triester method,60 N-benzoyl protection has been ap- 

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