A rigid molecular clip comprising bisphosphonate binding sites and aromaticsidewalls forming an electron-rich cavity is able to distinguish between nucleosides andnucleotides in aqueous solution. Neutral nucleosides as well as antibiotics derived thereofare drawn into the unpolar interior of the cleft and lead to substantial upfield-shifts in the 1HNMR spectrum. Nucleoside drugs can therefore be detected with high selectivity in thepresence of their phosphorylated pendants or nucleic acids.