Isosterism and Bioisosterism Case Studies with Muscarinic Agonists

Abstract

The synthesis and activity of enantiomerically pure analogues of pilocarpine and muscarinic agonists with the azabicyclo[2.2.1]heptane skeleton is described. Structure-activity relationships support a flexible model in which a coulombic interaction as well as two H-bonding interactions with the receptor are necessary for potent muscarinic agonist activity. In this context, a critical appraisal of the concepts of isosterism and bioisosterism is put forward, isosterism is redefined, and bioisosterism is discarded in favor of the new concept of bioanalogy.