| abstract |
A compound of formula (I): (I) wherein X represents O or S; R1 represents C1-6 alkyl, C3-8 cycloalkyl, C3-8 cycloalkylmethyl or C3-8 cycloalkenyl any of which optionally may be substituted by one or more methyl groups or halogen atoms or R1 represents aryl, substituted aryl, heteroaryl or substituted heteroaryl; R2 represents hydrogen, methyl, which may be in either the α or β configuration, or methylene; R3 and R4 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. |