To assess the effect of conformational mobility on receptor activity, the β-phenyl substituent of dopamine D1 agonist ligands of the phenylbenzazepine class,(±)-6, 6a, 7, 8, 9, 13b- hexahydro-5H-benzo [d] naphtho [2, 1-b] azepine-11, 12-diol (8), and its oxygen and sulfur bioisosteres 9 and 10, respectively, were synthesized as conformationally-restricted analogs of SKF38393, a dopamine D1-selective partial agonist. Compounds trans-8b, 9, and 10 ...