Objectives: Three defects have been identified in purine de novo synthesis (PDNS). Dephosphorylated substrates (imidazole ribosides) of the deficient enzymes are accumulated in body fluids in affected patients. The aim of this work was to investigate mass spectrometric properties of aminoimidazole ribosides related to the second half of PDNS. Methods: These aminoimidazole ribosides were synthesised and chemically characterised. Liquid chromatography- -mass spectrometry technique was applied for structural identification. MS analysis was carried out using an LCQ ion trap mass spectrometer (Finnigan MAT, San Jose, USA). Atmospheric pressure chemical ionization source was employed. Results: Synthesis yielded ribosides with more than 90% purity and obtained fragmentation spectra confirmed their identity. The imidazole ring loses its substituents in the form of small molecules (NH3, CO2 or CO) in mass spectrometry fragmentation. The N-succinocarboxamide group of succinylaminoimidazole carboxamide riboside (SAICAr) either loses water from the free carboxyl groups or breaks away as a whole. Opening of the imidazole ring was not observed for any compound. Conclusions: Characteristics described above can be useful for development of new methods for diagnosing of known as well as unrevealed defects of second part of PDNS.

        Key words: purine, de Novo synthesis, mass spectrometry.