Certain substituted polyketides, pharmac eutical compositions containing them and their use in treating tumors

A compound of formula I

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• where
• A is —CH═C(R1)CH2—, —CH2N(R2)CH2—, —CH2N(R2)C(O)—, —C(O)N(R2)CH2—, —CH2N(CO2R3)CH2— or —CH2N(COR2)CH2—;
• B is —CH(R1)CH═CHCH═CH2, —CH(R2)R1, —CH(R1)CH═CHR2, —CH(R1)CH═CHC(O)OR2, —CH(R1)CH═CHC(O)N(R1)R2, —CH(R1)CH2OR2 or Ar;
• C is H, —C(O)N(R1)R2, —C(O)NHCH2(CH2)nN(CH3)2, or —C(O)NHCH2(CH2)n-4-morpholino;
• R1 is H or (C1-6)alkyl;
• R2 is H, (C1-6)alkyl, (C2-6)alkenyl, (C2-6)alkynyl, (C1-6)alkyl-Ar or Ar;
• R3 is (C1-6)alkyl, (C1-6)alkyl-Ar or Ar;
• Ar is an aromatic or heteroaromatic ring selected from
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• R4 and R5 are, independently, H, (C1-6)alkyl, OH, O(C1-6)alkyl, OCH2(CH2)nOH, O(CH2)nCO2H, OCH2(CH2)nN(CH3)2, OCH2(CH2)n-4-morpholino, F, Cl, Br or CF3;
• and
• n is 1 or 2;
• with the proviso that when A is —CH═C(CH3)CH2— or —CH═CHCH2—,
• then either:
• B cannot be —CH(CH3)CH═CHCH═CH2, —CH(CH3)CH2Ph, —CH(CH3)Ph, —CH(CH3)-n-Bu,
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• or C cannot be —C(O)N(R1)R2 or H;
• or an acid or base addition salt thereof, where possible.