Table 4.

Biphenylpiperazine hit series 4 SAR determined in the human sperm calcium influx assay.^[a]

Compd	R1	R2	IC50 [μM]
4 a	m‐CF3	m‐CF3	4.9±0.6
4 b	p‐F	m‐CF3	8.9±0.4
4 c	m‐CF3	m‐Cl	6.0±0.4
4 d	m‐CF3	H	>100
4 e	H	m‐CF3	>100
4 f	m‐CF3	o‐CF3	>100
4 g	m‐CF3	p‐Me	>100
4 h	m‐CF3	p‐Cl	>100
4 i	m‐CF3	p‐OMe	>100
4 j	m‐Me	o‐CF3	>100
4 k	p‐Me	o‐CF3	>100
4 l	o‐Me	o‐CF3	64±18
4 m			39*
4 n			>100

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