| abstract |
A compound of formula (1), in which: X represents O or S; R 1 represents C 1-6 alkyl, C 3-8 cycloalkyl, C 3-8 cycloalkyl or C 3-8 cycloalkenyl, any of which may be optionally substituted with one or more methyl groups or halogen atoms or R 1 represents aryl, aryl substituted, heteroaryl or substituted heteroaryl; R2 represents hydrogen, methyl which may be in alpha or beta configuration, methylene; R3 and R4 are the same or different and each independently represent hydrogen, halogen or a methyl group; and "lines and period" represents a single or double bond; or a physiologically acceptable salt or solvate thereof. |