The current invention restates substituted indole nucleosides as both terminal as well as internal building blocks of labeled oligonucleotide probes for the detection, analysis and quantitation of nucleic acids. The substituent comprises a linker and a detectable group or a linker and a reactive group for post synthesis coupling. These modified nucleosides grant access to a wide application area. These new substituted indole nucleosides can be used as labeling reagents for the facile preparation of e.g. optimized hybridization probes, Taqman-probes, or molecular beacon probes.