Table 5.

Benzimidazolidin-2-iminium hit series 5 SAR determined in the human sperm calcium influx assay

Compound	R1	R2	IC50, μM
5a	p-Br		12 ± 2
5b	p-Br	Me	7.7 ± 0.1
5c	p-Br	H	19 ± 3
5d	H		71 ± 1
5e	p-OMe		> 100
5f	m-Br		3.4 ± 0.4
5g	H		9.8 ± 1.4
5h	p-OMe		12*
5i	m,p-(Cl)2		5.0 ± 1.1
5j	m,p-(Cl)2		4.1*
5k			14 ± 2

CatSper activated by 3 μM progesterone. IC₅₀ values are means ± SEM of 3 independent experiments.

^*IC₅₀ value is the mean of 2 independent experiments.