Structure-activity relationships of pyrimidine nucleotides containing a 5'-α,β-methylene diphosphonate at the P2Y₆...

The G_q-coupled P2Y₆ receptor (P2Y₆R) is a component of the purinergic signaling system and functions in inflammatory, cardiovascular and metabolic processes. UDP, the native P2Y₆R agonist and P2Y₁₄R partial agonist, is subject to hydrolysis by ectonucleotidases. Therefore, we have synthesized UDP/CDP analogues containing a stabilizing α,β-methylene bridge as P2Y₆R agonists and identified compatible affinity-enhancing pyrimidine modifications. A distal binding region on the receptor was explored with 4-benzyloxyimino cytidine 5'-diphosphate analogues and their potency determined in a calcium mobilization assay. A 4-trifluoromethyl-benzyloxyimino substituent in 25 provided the highest human P2Y₆R potency (MRS4554, 0.57 µM), and a 5-fluoro substitution of the cytosine ring in 28 similarly enhanced potency, with >175- and 39-fold selectivity over human P2Y₁₄R, respectively. However, 3-alkyl (31-33, 37, 38), β-d-arabinofuranose (39) and 6-aza (40) substitution prevented P2Y₆R activation. Thus, we have identified new α,β-methylene bridged N⁴-extended CDP analogues as P2Y₆R agonists that are highly selective over the P2Y₁₄R.