Debromination of ATRP-made Wang soluble polymer supports

End-functionalized polymers by controlled/living radical polymerizations: synthesis and applications

This review focuses on end-functionalized polymers synthesized by controlled/living radical polymerizations and the applications in fields including bioconjugate formation, surface modification, topology construction, and self-assembly.

Photocontrolled Synthesis of Abiotic Sequence-Defined Oligo(Phosphodiester)s

A photoregulated phosphoramidite iterative process is studied for the synthesis of non-natural, digitally encoded oligo(phosphodiester)s. The oligomers are prepared using two reactive phosphoramidite monomers containing a 2-(2-nitrophenyl)propoxycarbonyl (NPPOC) protected OH group. The stepwise synthesis is performed on an OH-functional soluble polystyrene support, which allows recycling by precipitation in a nonsolvent. Repeating cycles involving phosphoramidite coupling, oxidation of phosphite to phosphate, and NPPOC deprotection by light irradiation at λ = 365 nm are performed in order to prepare oligomers with different lengths and sequences. Synthesis is conducted on a micromolar scale and good recycling yields are obtained in all cases. The use of a soluble polymer support allows an in-depth characterization of the NPPOC photo-deprotection step by ¹ H NMR, UV spectroscopy, and size exclusion chromatography, and thus identification of optimal synthesis conditions. After cleavage from the support, the oligo(phosphodiester)s are characterized by tandem mass spectrometry, which confirms preparation of uniform sequence-coded oligomers.

Synthesis of oligoarylacetylenes with defined conjugated sequences using tailor-made soluble polymer supports

The use of polystyrene-based soluble polymer supports greatly simplifies the synthesis and characterization of self-aggregating sequence-defined oligoarylacetylenes.

Optimal ATRP-Made Soluble Polymer Supports for Phosphoramidite Chemistry

Soluble polystyrene supports with optimal molecular structures for iterative phosphoramidite chemistry were prepared by atom-transfer radical polymerization (ATRP) and subsequent chain-end modification steps. The controlled radical polymerization of styrene was first performed in the presence of an 9-fluorenylmethoxycarbonyl (Fmoc)-protected amino-functional ATRP initiator. Soluble supports of different molecular weight were prepared. Size-exclusion chromatography and NMR analysis indicated formation of well-defined polymers with controlled chain lengths and narrow dispersity. After synthesis, the bromo ω end group of the ATRP polymer was removed by dehalogenation in the presence of tributyltin hydride, and the Fmoc protecting group of the α moiety was subsequently cleaved with piperidine. The resulting α-primary amine was afterwards treated with a linker containing a carboxyl group, a cleavable ester site, and a dimethoxytrityl-protected hydroxyl group to afford ideal soluble supports for phosphoramidite chemistry. NMR analysis indicated that these chain-end modifications were quantitative. The supports were tested for the synthesis of a non-natural sequence-defined oligophosphates. High-resolution ESI-MS analysis of the cleaved oligomers indicated formation of uniform species, and thus confirmed the efficiency of the ATRP-made soluble polymer supports. In addition, the synthesis of a thymidine-loaded soluble support was achieved.