The application is directed to compounds of Formula I: and pharmaceutically acceptable salts and solvates thereof, wherein R1, R2, R3, R4a, and R4b are defined as set forth in the specification. The invention is also directed to use of compounds of Formula I 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.本發明關於式I化合物：及其醫藥上可接受之鹽和溶劑合物，其中R1、R2、R3、R4a和R4b係如說明書中所提出之定義。本發明亦關於式I化合物用於治療對一或多種類鴉片受體之調節有反應的失調或作為合成中間體的用途。本發明的特定化合物尤其可用於治療疼痛。
