We previously reported 1<i>H</i>-imidazo[4,5-<i>c</i>]quinolin-4-amines as A<sub>3</sub> adenosine receptor (A<sub>3</sub>AR) positive allosteric modulators (PAMs). A<sub>3</sub>AR agonists, but not PAMs, are in clinical trials for inflammatory diseases and liver conditions. We synthesized new analogues to distinguish 2-cyclopropyl antagonist <b>17</b> (orthosteric interaction demonstrated by binding and predicted computationally) from PAMs (derivatives with large 2-alkyl/cycloalkyl/bicycloalkyl groups). We predicted PAM binding at a hydrophobic site on the A<sub>3</sub>AR cytosolic interface. Although having low Caco-2 permeability and high plasma protein binding, hydrophobic 2-cyclohept-4-enyl-<i>N</i>-3,4-dichlorophenyl, MRS7788 <b>18</b>, and 2-heptan-4-yl-<i>N</i>-4-iodophenyl, MRS8054 <b>39</b>, derivatives were orally bioavailable in rat. 2-Heptan-4-yl-<i>N</i>-3,4-dichlorophenyl <b>14</b> and 2-cyclononyl-<i>N</i>-3,4-dichlorophenyl <b>20</b> derivatives and <b>39</b> greatly enhanced Cl-IB-MECA-stimulated [<sup>35</sup>S]GTPγS binding <i>E</i><sub>max</sub>, with only <b>12b</b> trending toward decreasing the agonist EC<sub>50</sub>. A feasible route for radio-iodination at the <i>p-</i>position of a 4-phenylamino substituent suggests a potential radioligand for allosteric site binding. Herein, we advanced an allosteric approach to developing A<sub>3</sub>AR-activating drugs that are potentially event- and site-specific in action.