Treatment or prophylaxis of proliferative conditions

A compound of formula (I):

• or pharmaceutically acceptable salt, ester, amide or solvate thereof, wherein:
• X1 is such that —X1—X2 is —O—X2, —S—X2, —SO2—O—X2, —SO2NZ10—X2, conjugated alkenemethyloxy or conjugated alkenemethylthio, conjugated alkenemethylSO2—O, conjugated alkenemethyl-SO2NZ10 or of the formula:
• —X2 is absent or is such that X1—X2-Effector is one of
• each n and m is independently 0 or 1;
• p is 0, 1 or 2;
• X3 is oxygen or sulfur and additionally, when m=0, may be SO2—O, SO2NZ10, conjugated alkenemethyloxy, conjugated alkenemethylthio, conjugated alkenemethyl-SO2—O or conjugated alkenemethyl-SO2NZ10
• each of Y1, Y2 and Y3 is carbon;
• Y4 is oxygen, sulfur, sulfoxide or sulfone;
• —Y5— is a single bond;
• each of Z1-Z4, where present, are independently selected from hydrogen , alkyl, alkenyl, alkynyl, aryl, aralkyl, alkyloxy, alkenyloxy, alkynyloxy, aryloxy, aralkyloxy, alkylthioxy, alkenylthioxy, alkynylthioxy, arylthioxy, aralkylthioxy, amino, hydroxy, thio, halo, carboxy, formyl, nitro and cyano;
• Z5, where present, is independently selected from hydrogen alkyl, alkenyl, alkynyl, aryl, aralkyl, alkyloxy, alkenyloxy, alkynyloxy, aryloxy, aralkyloxy, alkylthioxy, alkenylthioxy, alkynylthioxy, arylthioxy, aralkylthioxy, amino, hydroxy, thio, carboxy, formyl, nitro and cyano;
• or one of Z2 & Z3, Z3 & Z4 and Z4 and Z5 together with the atoms to which they are connected form an aromatic ring fused to the remainder of the compound;
• provided that at least one of Z1, Z2 and Z4 is hydrogen;
• Z6 is selected from hydrogen, alkyl, alkenyl, alkynyl, aryl and aralkyl;
• none, one or two of Y6 may be nitrogen atoms with the remainder being carbon atoms;
• each Z7 is independently hydrogen, alkyl or aryl;
• each Z8 is independently selected from hydrogen, an electron withdrawing group, unsubstituted C1-C6 alkyl, substituted C1-C6 alkyl, unsubstituted C1-C6 alkoxy, and substituted C1-C6 alkoxy where the substituted alkyl or alkoxy are substituted with one or more groups selected from ether, amino, mono- or di-substituted amino, cyclic C1-C5 alkylamino, imidazolyl, C1-C6 alkylpiperazinyl, morpholino, thiol, thioether, tetrazole, carboxylic acid, ester, amido, mono- or di-substituted amido, N-connected amide, N-connected sulfonamide, sulfoxy, sulfonate, sulfonyl, sulfoxy, sulfinate, sufinyl, phosphonooxy, phosphate and sulfonamide;
• each Z9 is independently oxygen or sulfur;
• Z10 is hydrogen or alkyl, for example a C1-4alkyl;
• and
• Effector is a molecule of formula (II);
• wherein:
• Z12 is oxygen or sulfur;
• each X4 is independently oxygen, sulfur or NZ13, wherein each —Z13 is independently —(CH2)2—Z14, -alkyl or -hydrogen;
• and
• each Z14 is independently chloro, bromo, iodo or mesylate.