title: [Studies on crystal structures and structure-activity relationships of the 4-substituted fentanyl derivatives].
mesh_terms: D000701:Analgesics, Opioid / Q000032:analysis*; D005283:Fentanyl / Q000031:analogs & derivatives* / Q000032:analysis; D008968:Molecular Conformation; D013329:Structure-Activity Relationship
chemical_list: D000701:Analgesics, Opioid; C056123:R 32557; C056122:R 32767; D005283:Fentanyl