DNA-porphyrin hybrids as reaction centers for photosensitized ene reactions with singlet oxygen

Abstract

Recent developments in DNA-mediated nanostructuring have paved the way for the development of novel reaction centers. As part of a project focused on nanostructured reaction centers for reactions catalyzed by porphyrins, we have developed a solid-phase synthesis of tetrakis(p-hydroxyphenyl)porphyrin-oligonucleotide hybrids. In these hybrids, up to four nucleic acid chains are linked to the phenolic substituents of the porphyrin via phosphodiester linkages. A representative hybrid with one oligonucleotide chain of the sequence TTAA was found to survive light irradiation under aerobic conditions for 2 h with less than 35% oxidation of the DNA chain. An assay measuring the diastereo- and enantioselectivity of the photosensitized ene reaction of mesitylol with singlet oxygen was set up that provides diastereomeric ratios via NMR of aliquots of the reaction solution. Enantiomers were separated gas chromatographically on a chiral stationary phase and were assigned based on the product distribution obtained with an enantiomerically enriched starting material. Our results are a starting point for the exploration of nanostructured reaction media based on DNA and porphyrins.