Synthesis of a new N1-pentyl analogue of cyclic inosine diphosphate ribose (cIDPR) as a stable potential mimic of cyclic ADP ribose (cADPR)

The new analogue 7 of cADPR (1), a cyclic nucleotide bis(phosphate) involved in Ca2+ metabolism, was prepared starting from 2′,-3′-isopropylideneinosine (8) which was alkylated at N-1, leading to the intermediate 11. Bis(phosphorylation) of 11 through two alternative procedures, followed by phosphate deprotection steps, afforded derivatives 15 and 16, the substrates for the intramolecular pyrophosphate bond formation. Both 15 and 16 were converted into derivative 17 in high yields, which was finally deprotected to give the target compound 7.