| abstract |
A compound of formula (I) or a pharmaceutically acceptable salt thereof: <CHEM> in which X represents R1OOC- in which R1 is C1-4 alkyl, C2-4 alkenyl or C2-4 alkynyl; R2O- in which R2 is C1-2 alkyl, C1-2 alkylcarbonyl or aminocarbonyl optionally substituted by one or two methyl groups; a group <CHEM> in which Y represents a 3-membered divalent residue completing a 5-membered aromatic ring and comprises one or two heteroatoms selected from oxygen, nitrogen and sulphur, any amino nitrogen optionally substituted by a C1-2 alkyl group, Y being optionally C-substituted by a methyl group; or a group <CHEM> in which A1 is oxygen or sulphur, one of A2 and A3 is CR3 and the other is nitrogen or CR4 where R3 and R4 are independently selected from hydrogen and methyl; and each of p and q independently represents an integer of 2 to 4. |