Abstract
The G(q)-coupled P2Y(6) receptor (P2Y(6)R) is a component of the purinergic signaling system and functions in inflammatory, cardiovascular and metabolic processes. UDP, the native P2Y(6)R agonist and P2Y(14)R partial agonist, is subject to hydrolysis by ectonucleotidases. Therefore, we have synthesized UDP/CDP analogues containing a stabilizing α,β-methylene bridge as P2Y(6)R 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 P2Y(6)R 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 P2Y(14)R, respectively. However, 3-alkyl (31-33, 37, 38), β-d-arabinofuranose (39) and 6-aza (40) substitution prevented P2Y(6)R activation. Thus, we have identified new α,β-methylene bridged N(4)-extended CDP analogues as P2Y(6)R agonists that are highly selective over the P2Y(14)R.