TABLE 1

Affinities of mono- and disubstituted adenine derivatives for adenine receptors in rat brain cortical membranes


	Compound	R²	R⁶	R⁸	R⁹	K_i ± SEM (or Inhibition of Radioligand Binding at 100 μM)^a
1	Adenine	H	H	H	H	0.0299 ± 0.0034 μM
2	1-Methyladenine					29.3 ± 9.3 μM
3	2-Fluoroadenine	F	H	H	H	0.62 ± 0.14 μM
4	2-Chloroadenine	Cl	H	H	H	37.9 ± 4.4 μM
5	3-Methyladenine					(5 ± 2%)
6	N⁶-Methyladenine	H	methyl	H	H	3.64 ± 0.36 μM
7	N⁶-Benzyladenine	H	benzyl	H	H	(30 ± 3%)
8	N⁶-Benzoyladenine	H	benzoyl	H	H	46.6 ± 15.3 μM
9	trans-Zeatin	H	(E)-CH₂CH=C(CH₃)CH₂OH	H	H	22.6 ± 2.1 μM
10	N⁶-Dimethyladenine					(11 ± 2%)
11	7-Methyladenine					4.13 ± 1.08 μM
12	7-Ethyladenine					47.3 ± 4.1 μM
13	8-Bromoadenine	H	H	Br	H	17.3 ± 2.7 μM
14	8-Thioadenine	H	H	SH	H	2.77 ± 0.12 μM
15	9-Methyladenine	H	H	H	methyl	17.5 ± 3.0 μM
16	9-Ethyladenine	H	H	H	ethyl	(27 ± 2%)
17	9-Dihydroxy-propyladenine	H	H	H	-CH₂CHOHCH₂OH	78.6 ± 14.6 μM