Discovery of a potent M antagonist with improved clearance profile. Part 2: Pyrrolidine amide-based antagonists.

This Letter describes our ongoing effort to improve the clearance of selective M antagonists. Herein, we report the replacement of the previously disclosed piperidine amide (4, disclosed in Part 1) with a pyrrolidine amide core. Several compounds within this series provided good potency, subtype selectivity, and low to moderate clearance profiles. Interestingly, the left-hand side SAR for this series diverged from our earlier efforts.