摘要 |
Compounds of formula I or pharmaceutically acceptable salts thereof Formula (I) wherein Ar, R<SUP>1</SUP>, R<SUP>2</SUP>, R<SUP>3</SUP>, R<SUP>a</SUP>, R<SUP>b </SUP>and X are as defined in the specification as well as salts and pharmaceutical compositions including the compounds are prepared. They are useful in therapy, in particular in the management of pain |