To explore the nature of the interaction between the cocaine receptor and high-affinity ligands as well as attempt to identify the proximal effect of electron-rich/unsaturated 2β-substituents, a series of 2β-substituted 3β-phenyltropanes were synthesized and tested in vitro for cocaine receptor affinity and for dopamine uptake inhibition. The 2β-substituted 3β-phenyltropane derivatives 5-10 were prepared from N-methyl-2β-carbomethoxy-3β-phenyltropane 2 (synthesized from cocaine) via LiAlH4 reduction, Swern oxidation, olefination, hydrogenation, and other reactions. The derivatives 6-10 were tested for their ability to displace bound [³H]-3 from rat caudate-putamen tissue and to inhibit high-affinity uptake of [³H]dopamine into rat caudate-putamen tissue. The results showed that the affinities of compounds 6-10 are generally similar to the high-affinity values of cocaine (1) and 2, with the saturated alcohol 9 exhibiting a 2-fold increase in potency in both in vitro assays. In conclusion, the stereochemical orientation of substituents at C2 is the primary requirement for high-affinity binding to cocaine receptors, while the steric bulk and lipophilic character of 2β-substituents have minimal effects on affinity. Furthermore, the structure-activity relationships (SAR) reported here support the hypothesis that electrostatic interactions (including hydrogen bonds) between 2β-substituents and the cocaine binding site are of minimal importance, whereas hydrophobic interactions may significantly contribute to the free energy of binding and enhance ligand potency.