Table 1. Bioisosteric Replacement of the Piperidyl Amide Fragment: In Vitro hmGluR5 Antagonism.

compd	R1	R3	R2	IC50 [μM]a
2				0.064
7a	−(CH2)4−		H	1.2
7b	Me	Me	H	48% @ 10
7c	Me	H	Me	2.9
7d	Pr	H	Me	0.23
7e	Pr	Me	Me	0.25
15a	Pr	−phenyl−b		0.18

^ahmGluR5 Ca²⁺ flux⁷ using glutamate as agonist; data are geometric means of n ≥ 2.

^bBenzimidazole.