Opioid analgesics are clinically used to relieve severe pain in acute postoperative and cancer pain, and also in the long term in chronic pain. The analgesic action is mediated by μ-, δ-, and κ-receptors, but currently, with few exceptions for k-agonists, μ-agonists are the only ones used in therapy. Previously synthesized compounds with diazotricyclodecane cores (DTDs) have shown their effectiveness in binding opioid receptors. Fourteen novel diazatricyclodecanes belonging to the 9-propionyl-10-substituted-9,10-diazatricyclo[4.2.1.12,5]decane (compounds 20–23, 53, 57 and 59) and 2-propionyl-7-substituted-2,7-diazatricyclo[4.4.0.03,8]decane (compounds 24–27, 54, 58 and 60) series, respectively, have been synthesized and their ability to bind to the opioid μ-, δ- and κ-receptors was evaluated. Five of these derivatives, compounds 20, 21, 24, 26 and 53, showed μ-affinity in the nanomolar range with a negligible affinity towards δ- and κ-receptors and high μ-receptor selectivity. The synthesized compounds showed μ-receptor selectivity higher than those of previously reported methylarylcinnamyl analogs.