A new analogue 1 of cADPR was prepared through a synthetic pathway starting from 6-chloropurine 2 which underwent two sequential alkylations at N-9 and N-1, with formation of the intermediate 8. The successive bis-phosphorylation of hydroxyalkyl functions, followed by deprotection and reprotection steps, afforded the derivative 13, the substrate for the cyclization reaction. This was carried out according to the Matsuda procedure and led to the intramolecular pyrophosphate bond formation, thus affording 14. The ®nal deprotection of 14, in alkaline conditions, gave the target compound 1 in good yield.