Table 1.

Guanidinium hit series 1 SAR determined in the human sperm calcium influx assay.^[a]

Compd	R1	R2	IC50 [μM]
1 a		H	5.4±0.6
1 b		H	9.1±0.4
1 c		H	67±12
1 d		H	>100
1 e			23±6
1 f			7.8*
1 g			>100
1 h			26*
1 i			8.1*
1 j			>100*

[a] CatSper activated by 3 μM progesterone. IC₅₀ values are means±SEM of three independent experiments. *IC₅₀ values are means of two independent experiments.