Protecting Groups in Oligonucleotide Synthesis

A biopolymer is synthesized by assembling monomeric or oligomeric blocks. Each block features at least a nucleophilic and an electrophilic function, i.e., the α-amino and the carboxylic functions for peptides, the 5′-OH and the 3′-function (phosphate, phosphoramidite, or phosphonate), for nucleotides. The nucleophilic and electrophilic sites are linked together at the coupling step. Protection is a necessity. It guarantees the chemoselectivity of coupling and the solubility of synthons in organic solvents.