A synthetic cyclitol-nucleoside conjugate polyphosphate is a highly potent second messenger mimic

Reactions that form sec - sec ethers are well known, but few lead to compounds with dense functionality around the O -linkage. Replacement of the α-glucopyranosyl unit of adenophostin A, a potent d - myo -inositol 1,4,5-trisphosphate (IP 3 R) agonist, with a d - chiro -inositol surrogate acting substantially as a pseudosugar, leads to " d - chiro -inositol adenophostin". At its core, this cyclitol-nucleoside trisphosphate comprises an ether linkage between the axial 1-hydroxyl position of d - chiro -inositol and the 3′-hydroxyl group of an adenosine ribose sugar. A divergent synthesis of d - chiro -inositol adenophostin has been achieved. Key features of the synthetic strategy to produce a triol for phosphorylation include a new selective mono-tosylation of racemic 1,2:4,5-di- O -isopropylidene- myo -inositol using tosyl imidazole; subsequent conversion of the product into separable camphanate ester derivatives, one leading to a chiral myo -inositol triflate used as a synthetic building block and the other to l -1- O -methyl- myo -inositol [ l -(+)-bornesitol] to assign the absolute configuration; the nucleophilic coupling of an alkoxide of a ribose pent-4-ene orthoester unit with a structurally rigid chiral myo -inositol triflate derivative, representing the first sec - sec ether formation between a cyclitol and ribose. Reaction of the coupled product with a silylated nucleobase completes the assembly of the core structure. Further protecting group manipulation, mixed O - and N -phosphorylation, and subsequent removal of all protecting groups in a single step achieves the final product, avoiding a separate N 6 protection/deprotection strategy. d - chiro -Inositol adenophostin evoked Ca 2+ release through IP 3 Rs at lower concentrations than adenophostin A, hitherto the most potent known agonist of IP 3 Rs. A densely functionalised phosphorylated chiro -inositol-nucleoside ether conjugate constructed from cyclic fragments is the most potent IP 3 receptor ligand discovered.