Table 1.

Potencies of various uridine 5’-diphosphate (UDP) and α,β-methylene-UDP analogues in comparison to known UDP derivatives for activation of the human P2Y₆R, as determined in an assay of calcium mobilization, unless noted.^a

Compound	x =	Y =	Z =	P2Y6R, EC50, μM (Ca2+, unless noted)
5′-Diphosphates
1 UDP	H	H	O	0.0416±0.007
2	I	H	O	0.0491±0.0195, 0.015±0.002b
11	H	H	NOCH3	0.493±0.128
12	H	H	NNHCOOCH3	1.54f
13	H	H	NOCH2C6H5	0.793±0.149
5′-α,β-Methylene diphosphonates
14ac	H	H	O	0.70±0.11b
15c	I	H	O	0.0491±0.0195,c 0.13±0.02b
16c	F	H	O	0.203 ± 0.030c
17c	Cl	H	O	0.097 ± 0.011
18c	Br	H	O	0.104 ± 0.010
9	H	H	NOCH3	0.42±0.08d
10	H	H	NOCH2C6H5	2.36±0.73d
19	H	H	NOCH2C6H5-3-F	2.70 ± 0.78
20	H	H	NOCH2C6H5-3-Cl	1.45 ± 0.22
21	H	H	NOCH2C6H5-3-CF3	1.91 ± 0.47
22	H	H	NOCH2C6H5-3-CO2CH3	0.902 ± 0.05
23	H	H	NOCH2C6H5-4-Cl	1.32 ± 0.08
24	H	H	NOCH2C6H5-4-CH3	5.12 ± 0.28
25c	H	H	NOCH2C6H5-4-CF3	0.571 ± 0.196
26	H	H	NOCH2C6H5-4-CO2CH3	1.67 ± 0.34
27	H	H	NOCH2C6H5-4-SF5	1.59 ± 0.09
28c	F	H	NOCH2C6H5	0.549 ± 0.070
29c	CH3	H	NOCH2C6H5	1.09 ± 0.32
30c	H	H	N4-CO-Ph	1.39 ± 0.223c
Inactive (% activation at 3 μM of <10%)
31c	H	CH2CH3	O	3.5%
32c	H	(CH2)2CH3	O	2.7%
33c	H	CH2C6H5	O	5.3%
34c	F	-	-	5.7%
35c	I	-	-	3.4%
36c	CH3	-	-	3.0%
37c	H	CH3	NOCH2C6H5	3.6%c
38c	H	CH2CH3	NOCH2C6H5	5.7%
Other inactives (% activation at 3 μM of <10%)
39c	Structure shown in footnotee			2.4%
40c	Structure shown in footnotee			5.2%

^aAgonist potencies reflect P2Y₆R-dependent calcium mobilization in 1321N1 human astrocytoma cells stably expressing the human P2Y₆R. Potencies are presented in the form of EC₅₀ values, which represent the concentration of agonist at which 50% of the maximal effect on calcium mobilization is achieved. These values were determined using a four-parameter logistic equation and the GraphPad software package (GraphPad, San Diego, CA). The results are presented as mean ± standard error and are the average of three to six different experiments, unless noted, with each molecule.

^bEC₅₀ values from Maruoka et al. (PLC assay).⁴

^cAll syntheses for indicated compounds were reported in Junker et al., as well as the P2Y₆R Ca²⁺ assay results for compound 30.³³

^dReported in Toti et al. (Ca²⁺ assay).³

^eStructures of 39: 40:

^fn = 1 (tested once).