Nitroxide‐Derived N‐Oxide Phenazines for Noncovalent Spin‐Labeling of DNA

Abstract

Two o‐benzoquinone derivatives of isoindoline were synthesized for use as building blocks to incorporate isoindoline nitroxides into different compounds and materials. These o‐quinones were condensed with a number of o‐phenylenediamines to form isoindoline‐phenazines in high yields. Subsequent oxidation gave phenazine‐di‐N‐oxide isoindoline nitroxides that were evaluated for noncovalent and site‐directed spin‐labeling of duplex DNA and RNA that contained abasic sites. Although only minor binding was observed for RNA, the unsubstituted phenazine‐N,N‐dioxide tetramethyl isoindoline nitroxide showed high binding affinity and selectivity towards abasic sites in duplex DNA that contained cytosine as the orphan base.