| abstract |
A compound of formula (I): n nwhereinn X represents O or S; R 1 represents C 1-6 alkyl, C 3-8 cycloalkyl, C 3-8 cycloalkylmethyl or C 3 - 8 cycloalkenyl any of which optionally may be substituted by one or more methyl groups or halogen atoms or R 1 represents aryl, substituted aryl, heteroaryl or substituted heteroaryl; R 2 represents hydrogen, methyl, which may be in either the α or β configuration, or methylene; R 3 and R 4 are the same or different and each independently represents hydrogen, halogen or a methyl group; and represents a single or a double bond; or a physiologically acceptable salt or solvate thereof. |