Table 2. Optimization of Benzimidazole Fragment: In Vitro hmGluR5 Antagonism.

| compd | R1 | 4-W | 5-W | 6-W | 7-W | IC50 [μM]a | HLMb | RLMb |
|---|---|---|---|---|---|---|---|---|
| 15b | Pr | H | H | H | H | 0.10 | 83 | 158 |
| 15c | Et | H | H | H | H | 0.11 | 120 | 118 |
| 15d | Bu | H | H | H | H | 0.36 | 347 | 279 |
| 15e | iBu | H | H | H | H | 0.11 | 55 | 826 |
| 15f | Pr | Cl | H | H | H | 0.20 | 74 | 69 |
| 15g | Pr | H | Cl | H | H | >0.5 | 400 | 34 |
| 15h | Pr | H | H | Cl | H | 0.13 | 56 | 33 |
| 15i | Pr | H | H | H | Cl | 0.024 | 83 | 112 |
hmGluR5 Ca2+ flux7 using glutamate as agonist; data are geometric means of n ≥ 2.
HLM: human liver microsomes. RLM: rat liver microsomes. CLint (intrinsic clearance) reported in μL/min/mg protein.