A rigid mol. clip comprising bisphosphonate binding sites and arom. sidewalls forming an electron-rich cavity is able to distinguish between nucleosides and nucleotides in aq. soln. Neutral nucleosides as well as antibiotics derived thereof are drawn into the unpolar interior of the cleft and lead to substantial upfield shifts in the 1H NMR spectrum. Nucleoside drugs can therefore be detected with high selectivity in the presence of their phosphorylated pendants or nucleic acids.