A compound, or solvate or salt thereof, of formula ##STR1## R.sub.1 is hydrogen, halogen, or C.sub.1-6 alkyl; R.sub.2 and R.sub.3 are hydrogen or C.sub.1-6 alkyl; R.sub.5 together with R.sub.4 forms a --(CH).sub.2).sub.2 -- group optionally substituted by one or two C.sub.1-6 alkyl; W is halogen or when A is gem-dimethyl substituted piperidine, is OH; a is 1 or 2, useful in the treatment of pain.
化合物的分子式为##STR1## 其中R.sub.1为氢、卤素或C.sub.1-6烷基;R.sub.2和R.sub.3为氢或C.sub.1-6烷基;R.sub.5与R.sub.4一起形成一个-(CH).sub.2).sub.2-基团,可选地被一个或两个C.sub.1-6烷基取代;W为卤素或当A为双甲基取代的
哌啶时,为OH;a为1或2,可用于治疗疼痛。