Synthesis of solvatofluorochromic 7-arylethynylated 7-deaza-2′-deoxyadenosine derivatives: application to the design of environmentally sensitive fluorescent probes forming stable DNA duplexes

We synthesized environmentally sensitive fluorescent (ESF) 7-deaza-2′-deoxyadenosine derivatives including ethynylanthracene substituted atzA (1) and ethynylnaphthalene substituted nzA (2a), cnzA (2b), anzA (2c), and dnzA (2d), and investigated their photophysical properties. Among them, only push–pull type cyano- and acetyl-substituted naphthylethynylated 7-deaza-2′-deoxyadenosine, cnzA (2b) and anzA (2c), exhibited remarkable solvatofluorochromic properties (Δλ = 71 and 63 nm, respectively). We incorporated non-solvatofluorochromic atzA (1) and solvatofluorochromic cnzA (2b) into oligodeoxynucleotides and found that cnzA (2b) forms a stable base pair with both thymine and cytosine, being accompanied by a change of fluorescence intensity. Such ESF nucleosides can be used for studying structures and functions of nucleic acids.