Photoresponsibility of oligonucleotides containing 5-vinyl-2'-deoxyuridine derivatives having an aromatic group and its selectivity for 5-methylcytosine (C-m) were evaluated. Their high extinction coefficient and hydrophobicity caused C-m selective photoligation with a 10- to 20-fold higher reaction rate than 5-cyanovinyl-2'-deoxyuridine, previously reported.