While the function of NAD+ as energy transducer has been well established, it is also now known to play an important role in cellular processes such as gene regulation and cell maintenance. In addition; NAD is a precursor to biologically active metabolites such as ADPR, ADP_ribosyl-derivatives and cADPR. cADPR is a Ca 2 -modulating second messenger formed by the cyclisation of NAD+ by ADP-ribosyl cyclases. While three different enzymes have been identified as cyclases, the mechanism and site of activity of such enzymes has not yet been fully established. The aim of this work is thus to synthesise base-modified NAD+ analogues that can reach the cyclase active site, and be enzymatically converted to cyclic products that fluoresce at wavelengths not harmful to cells. Such analogues may facilitate establishing the location and mechanism of the cyclase and also the metabolic pathway of cADPR. Nine novel n~cleosides were synthesised by glycosylation of the selected heterocycles with a protected ribose using Vorbriiggen conditions. Subsequent phosphorylation using PM chemistry developed by Yoshikawa afforded the nucleotide analogues. Fluorescence studies of the nucleosides were then carried out to provide preliminary information as to whether any of the analogues would fluoresce, and at which excitation and emission wavelengths the fluorescence would occur. This synthetic route was designed to introduce the relatively unstable nicotinamide moiety at the final step. However, coupling to nicotinamide mononucleotide to form the cyclic precursors proved unfruitful, despite subjection to numerous different reaction conditions.