Position 6 of the morphinan skeleton plays a key role in the -opioid receptor (MOR) activity in vitro and in vivo. We describe the consequence of the 6-carbonyl group deletion in N-methylmorphinan-6-ones 1−4 on ligand−MOR interaction, signaling, and antinociception. While 6-desoxo compounds 1a, 2a, and 4a show similar profiles to their 6-keto counterparts, the 6-desoxo-14-benzyloxy substituted 3a displays significantly increased MOR binding and agonist potency and a distinct binding mode compared with its analogue 3.