U compound of formula (I) ** Formula ** or a pharmaceutically acceptable salt, solvate or polymorph thereof, including all tautomers and stereoisomers thereof: R1 represents C1-12 alkyl； C2-12 alkenyl, in which the double bond is not adjacent to nitrogen； C3-12 carbocyclyl； -C 1-6 alkyl-C3-12 carbocyclyl； C3-12 heterocyclyl； -C 1-6 alkyl-C 3-12 heterocyclyl； C6-12 aryl； C5-12 heteroaryl； C1-6 alkyl-C6-12 aryl； -C 1-6 alkyl-C5-12 heteroaryl； -phenyl condensed to C3-12 carbocyclyl or -phenyl condensed to C3-12 heterocyclyl； wherein any of the C3-12 carbocyclyl and C3-12 heterocyclyl groups mentioned above may be optionally substituted with one or more groups selected from methyl and oxo； and wherein any of the aforementioned phenyl, C6-12 aryl and heteroaryl C5-12 groups may be optionally substituted with one or more substituents selected from C1-6 alkyl, C2-6 alkenyl, C2-6 alkynyl, C1 haloalkyl -6, -C 1-6 thioalkyl, -SO 2 C 1-4 alkyl, C 1-6 alkoxy, -O-C 3-8 cycloalkyl, C 3-8 cycloalkyl, -SO 2 C 3-8 cycloalkyl, C 3-6 alkenyl-C3 alkynyl -6-oxy-, -C (O) C1-6 alkyl, C1-6 alkoxy-C1-6 alkyl, nitro, halogen, cyano, hydroxyl, -C (O) OH, -NH2, -N C1-4alkyl , -N (C1-4 alkyl) (C1-4 alkyl), -C (O) N (C1-4 alkyl) (C1-4 alkyl), - C (O) NH2, -C (O) NH (alkyl C 1-4), -C (O) C 1-6 alkyl, -C 1-4 alkyl and -C 3-6 cycloalkyl； or R1 represents phenyl substituted with phenyl, or phenyl substituted with an optionally substituted monocyclic C5-12 heteroaryl group in which any of the aforementioned monocyclic C5-12 heteroaryl groups may be optionally substituted with one or more groups selected from C1 alkyl -4, halogen and C1-4 alkoxy； or R1 represents benzyloxy-substituted phenyl in which any of the phenyl or benzyloxy groups may be optionally substituted on the ring with one or more groups selected from C1-4 alkyl, halogen and C1-4 alkoxy； and A represents in which Y represents a C2-5 alkylene chain, which may be optionally substituted with one or two methyl groups or may be optionally su
