What is claimed is: 1: A compound of formula (I): wherein R1 is a phenyl group which may be optionally substituted; R2 is selected from hydrogen, C1-6alkyl and ???(CH2)q???C3-7cycloalkyl; R3 is the group ???NH???CO???R4; R4 is selected from hydrogen, C1-6alkyl, C1-6alkoxy, ???(CH2)q???C3-7cycloalkyl, trifluoromethyl, ???(CH2)rphenyl optionally substituted by R5 and/or R6, ???(CH2)rheteroaryl optio