EN
Five different di-O-alkylated pentaerythritol phosphoramidite building blocks (2a–e) were synthesized and introduced into oligonucleotides to obtain mass-tagged probes (6a–f) useful in RNA transcription profiling. These non-nucleosidic mass tags allow categorization of oligonucleotide probes having identical nucleoside content and, hence, identification of the probe hybridized to RNA by mass spectrometry analysis. Hybridization properties of the oligonucleotide conjugates were elucidated by melting temperature measurements.