Potential neuroleptic agents. 3. Chemistry and antidopaminergic properties of substituted 6-methoxysalicylamides

A series of substituted 6-methoxysalicylamides were synthesized from their corresponding 2,6-dimethoxybenzamides by demethylation of one methoxy group with boron tribromide. Substituted 6-methoxysalicylamides having a lipophilic aromatic substituent in the 3-position para with respect to the methoxy group, e.g. a bromo or an iodo atom or an ethyl or a propyl group, and having an (S)-N-(1-alkyl-2-pyrrolidinyl)methyl moiety as the side chain were found to be potent blockers of [3H]spiperone binding in vitro and potent inhibitors of the apomorphine syndrome in the rat. Similar to remoxipride but in contrast to haloperidol, some of the substituted salicylamides show a 10-20-fold separation between the dose that inhibits hyperactivity and that which inhibits stereotypy. It was concluded that, besides the requirement of a lipophilic substituent in the position para to the methoxy group for antidopamine activity in vivo, the formation of a coplanar six-membered pseudoring involving the amide moiety and the methoxy group is a structural requirement for activity in vitro.