There are provided according to the invention compounds of formula (I) wherein R.sub.1 represents C.sub.1-6 alkyl or C.sub.1-6 haloalkyl; R.sub.2 represents --C(.dbd.O)-aryl or --C(.dbd.O)-heteroaryl; R.sub.3 represents hydrogen, methyl (which may be in either the .alpha. or .beta. configuration) or methylene; R.sub.4 and R.sub.5 are the same or different and each represents hydrogen or halogen; and----represents a single or a double bond; and salts and solvates thereof. There are also provided processes for preparing compounds of formula (I) and use of the compounds in therapy especially in the treatment of inflammatory and allergic conditions.