Orthogonal Synthesis of “Easy-to-Read” Information-Containing Polymers Using Phosphoramidite and Radical Coupling Steps

A new orthogonal solid-phase iterative strategy is proposed for the synthesis of sequence-coded polymers. This approach relies on the use of two successive chemoselective steps: (i) phosphoramidite coupling, and (ii) radical–radical coupling. These repeated steps can be performed using two different types of building blocks, i.e. a phosphoramidite monomer that also contains an alkyl bromide and a hydroxy-functionalized nitroxide. The phosphoramidite and the hydroxy group are reacted in step (i), thus leading to a phosphite that is oxidized in situ into a phosphate bond. The alkyl bromide is activated by copper bromide in step (ii) to afford a carbon-centered radical that is spin-trapped in situ by the nitroxide. The iterative repetition of these steps allow synthesis of uniform polymers, as evidenced by high-resolution electrospray mass spectrometry. Moreover, binary information could be easily implemented in the polymers using different types of phosphoramidite monomers in step (i). Interestingly, it was found that the formed information-containing polymers are very easy to sequence by tandem mass spectrometry due to the presence of easily cleavable alkoxyamine bonds formed in step (ii).