Photolabile Protecting Groups for Nitroxide Spin Labels

Abstract

Abstract Nitroxide spin labels can be protected against critical conditions of DNA/RNA or peptide synthesis by reduction and alkylation with light‐sensitive groups such as nitrobenzyl‐ or aminocoumarins. High chemical stability qualifies tetraethylisoindoline 5 and, with some restrictions, (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxy (TEMPO) precursor 4 as building blocks for spin‐labeled biopolymers. The yield of recovered nitroxides (80–95 %) is sufficient for PELDOR experiments. A protected TEMPO phosphoramidite was successfully used to synthesize a short spin‐labeled DNA with high yield and purity.