On resin click-chemistry-mediated synthesis of novel enkephalin analogues with potent anti-nociceptive activity

Here, we report the chemical synthesis of two DPDPE analogues 7a ( NOVA1) and 7b ( NOVA2 ). This entailed the solid-phase synthesis of two enkephalin precursor chains followed by a Cu I -catalyzed azide-alkyne cycloaddition, with the aim of improving in vivo analgesic efficacy versus DPDPE. NOVA2 showed good affinity and selectivity for the μ-opioid receptor (K I of 59.2 nM, EC 50 of 12.9 nM, E Max of 87.3%), and long lasting anti-nociceptive effects in mice when compared to DPDPE.