Fluorescent labeled reporter compounds having a modified cyanine dye that is coupled to a nucleotide derivative through a linker are disclosed. The compounds are useful for nucleic acid sequence analysis. The fluorescent labeled reporter compounds are ring-locked cyanine dyes that are coupled to a nucleotide derivative, such as a modified DNA base, through a linker. These fluorescent labeled reporter compounds can be used as DNA chain-terminators in DNA synthesis to generate DNA fragments that are fluorescently-labeled at the 3'-terminal end of the DNA fragment.