The application is directed to compounds of Formula I-A and pharmaceutically acceptable salts and solvates thereof, wherein Cy, R1a-R3a, R4a, and R4b are defined as set forth in the specification. The invention is also directed to use of compounds of Formula I-A to treat disorders responsive to the modulation of one or more opioid receptors, or as synthetic intermediates. Certain compounds of the present invention are especially useful for treating pain.