The application is directed to compounds of formula (I): and pharmaceutically acceptable salts, radiolabeled isomers, solvates, or hydrates thereof, wherein R1, R2, R3, X, and n are defined as set forth in the specification. The application is also directed to compounds of formulae II, I-a, I-a1, I-a2, I-b, and I-b1 and the pharmaceutically acceptable salts, radiolabeled isomers, solvates, and hydrates thereof. The application is also directed to use of Compounds of the present disclosure to treat disorders responsive to the modulation of one or more opioid receptors, or as synthetic intermediates. Certain Compounds of the present disclosure are especially useful for treating pain. In one embodiment, Compounds of the present disclosure exhibit less opioid-induced side effects (such as, euphoria or drug-liking).