A compound for use in the treatment of proliferative disorders, such as cancer, having the following formula: wherein: R1, R2 and R3 are independently H or lower alkyl; R4, R5, R6, R7 and R8 are independently H, halo, lower alkyl or —O-lower alkyl, provided that at least one is —O-lower alkyl; or at least one pair of R4 to R8, the members of which pair are adjacent to one another on the ring, are conjoined to form —O—(CR14R15)n—O—, where n is 1 or 2 and R14 and R15 are independently H or lower alkyl, and the remainder of R4 to R8 are independently H, halo, lower alkyl or —O-lower alkyl; and R9, R10, R11, R12 and R13 are independently H, halo, lower alkyl or —O— lower alkyl, provided that at least one is —O-lower alkyl; or at least one pair of R9 to R13, the members of which pair are adjacent to one another on the ring, are conjoined to form —O—(CR16R17)m—O—, where m is 1 or 2 and R16 and R17 are independently H or lower alkyl, and the remainder of R9 to R13 are independently H, halo, lower alkyl or —O-lower alkyl.