A compound of general formula (I): wherein Xi is H or COR1 and X2 is H or COR2 but X1 and X2 are not both H； R1 and R2 are the same or different and are each C1-4 alkyl substituted with R3, or a four to seven-membered ring which can be optionally substituted with R8 and can contain one or more additional heteroatoms selected from O, S(O)n and NR9； R3 is F, CF3, OR4, NR5R6 or S(O)nR7； R4, R5 and R6 are the same or different and are each H or C1-4 alkyl optionally substituted with R3, or NR5R6 is a C4-6 heterocycloalkyl ring containing one or more heteroatoms selected from O, NR8 and S(O)n； each n is 0-2； R7 is C1-4 alkyl； R8 is as defined for R3 or C1-4 alkyl optionally substituted with R3 or halogen； R9 is H or C1-4 alkyl； Y is NR9R10R11； and R10 and R11, are the same or different and are each H or C1-6 alkyl optionally substituted with R3 or halogen, or NR10R11, is a four to seven membered ring which can be optionally substituted with R8 or COR1, and can contain one or more additional heteroatoms selected from O, S(O)n and NR9； and hydrates thereof.
