The third company, Pfizer, discovered a benzylamino quinuclidine structure, which was called CP-96345 (figure 1). CP-96345 has a rather simple structure, composed of a rigid quinuclidine scaffold containing a basic nitrogen atom, a benzhydril moiety and an o-methoxy-benzylamine group. This compound showed high affinity for the NK1 receptor, but it also interacted with Ca2+ binding sites. Strongly basic quinuclidine nitrogen on the compound was considered to be responsible for this Ca2+ binding, which caused a number of systemic effects, unrelated to the blocking of the NK1 receptor. For that reason and also to simplify the structure, alkylation at this site was performed to produce analogs.