Table 1. Affinity (pK_i) and Potency (pEC₅₀) of Extended BnOCPA Derivatives at Human A₁R^a.

compd	R1	R2	pEC50 (hA1R)b	Emaxc	pKi (hA1R)d
BnOCPA	–CH2OH	H	8.43 ± 0.09	51.49 ± 1.9	6.18 ± 0.09
15	–CH2OH	p-i-Pr	7.87 ± 0.16	51.95 ± 3.1	5.77 ± 0.08
16	–CH2OH	p-t-Bu	8.20 ± 0.13	54.59 ± 2.8	5.58 ± 0.10
17	–CH2OH	p-CN	7.40 ± 0.19	58.03 ± 4.2	5.85 ± 0.06
18	–CH2OH	p-CONH2	7.71 ± 0.13	59.51 ± 4.1	5.98 ± 0.05

^aData are the mean ± SEM of at least three independent repeats conducted in duplicate.

^bThe negative logarithm of the agonist concentration required to produce a half-maximal inhibition response of the 10 μM forskolin-induced cAMP accumulation in CHO-K1-A₁R cells.

^cThe % maximal inhibition of cAMP accumulation for each agonist. Calculated as the % inhibition of the 10 μM forskolin response.

^dBinding affinity (pK_i) determined through the NanoBRET binding assay in HEK293 cells stably expressing human Nluc-A₁R. The resulting concentration-dependent decrease in NanoBRET ratio at 10 min was used to calculate pK_i. Statistical significance (*p < 0.05) determined using one-way ANOVA and Dunnett’s post-test and presented as described by Curtis et al.³¹