In recent years there has been substantial interest in the 14-aminodihydromorphinone derivatives methoclocinnamox (MC-CAM) and clocinnamox (C-CAM). To investigate the importance of the cinnamoyl ring substituent, a series of analogues have been prepared with chloro, methyl, and nitro substituents in the 2' and 4' positions. Despite some discrepancies between the in vitro and in vivo data, a clear SAR could be observed where the 2'-chloro and 2'-methyl ligands consistently displayed higher efficacy than their 4'-substituted analogues. The new series also followed the well-established SAR that 17-methyl ligands have greater efficacy at the mu opioid receptor than their 17-cyclopropylmethyl counterparts.