ABSTRACT: A large series of derivatives and analogues of the uracil nucleotides UMP, UDP, and UTP with modifications in various positions of the uracil moiety and/or the phosphate groups were synthesized and evaluated at human P2Y2, P2Y4, and P2Y6 receptors. 2--(Ar) alkylthio substitution of UMP and UDP was best tolerated by the P2Y2 receptor. 2-Phenethylthio-UMP (13e) showed an EC50 value of 1.3 μM at P2Y2 and> 70- ...