Novobiocin analogues as anticancer agents

The compounds according to Formula I

• wherein R1 is hydrogen, alkyl, alkenyl, alkynyl, carbocyclic, heterocyclic, aryl, aralkyl, carboxyl, amido, amino, sulfanyl, sulfenyl, sulfonyl, or ether;
• or R1 together with X2 and the atom to which R1 is attached form a heterocyclic ring having 4 to 8 ring members with at least one heteroatom selected from oxygen or nitrogen;
• or R1 together with X4 and the atom to which R1 is attached form a heterocyclic ring having 4 to 8 ring members with at least one heteroatom selected from oxygen or nitrogen;
• wherein R2 is hydrogen or hydroxy;
• wherein R3 is hydrogen or hydroxy;
• wherein R4 is hydrogen, methyl, hydroxy, carboxyl, —R12—O—R13, or —R12—R14,
• wherein R12 is a covalent bond or alkyl, and R13 is C-amido or acyl, and R14 is N-amido, —POR15R16, —SO2R17, or sulfonamido and wherein R15, R16, R17 are independently alkoxy;
• wherein R5 is hydrogen, alkyl, alkenyl, alkynyl, aryl, or aralkyl;
• wherein R6 is hydrogen, alkyl, alkenyl, alkynyl, aryl, aralkyl, alkoxy, aryloxy, or aralkoxy;
• wherein X1 is —O—, —CO—, or —N—;
• wherein X2 is —O—, —N—, —NR18—, —CR19—, or —CO—,
• wherein R18 and R19 is hydrogen, alkyl, alkenyl, alkynyl;
• or X2 together with R1 and the atom to which R1 is attached form a heterocyclic ring having 4 to 8 ring members with at least one heteroatom selected from oxygen or nitrogen;
• wherein X4 is —O—, —CR20—, —CO—, or —N—, wherein R20 is hydrogen, alkyl, alkenyl, alkynyl, or wherein X4 together with R1 and the atoms to which they are attached form a heterocyclic ring having 4 to 8 ring members with at least one heteroatom selected from oxygen or nitrogen;
• wherein X5, is —CR21— or —N—, wherein R21 is hydrogen, alkyl, alkenyl, alkynyl;
• wherein X6, is —CR22— or —N—, wherein R22 is hydrogen, alkyl, alkenyl, alkynyl, alkoxy, aryl, aralkyl, halogen, or nitro;
• or X6 together with X9 and the carbon at position 7 form a heterocyclic ring having 4 to 8 ring members with at least one heteroatom selected from oxygen or nitrogen;
• wherein X8, is —CR23— or —N—, wherein R23 is hydrogen, alkyl, alkenyl, alkynyl;
• wherein X9 is alkyl, alkenyl, alkynyl, ether, secondary or tertiary amino, or sulfanyl;
• or X9 together with X6 and the carbon at position 7 form a heterocyclic ring having 4 to 8 ring members with at least one heteroatom selected from oxygen or nitrogen;
• and wherein at least one of X1, X2, X4, X5, X6, X8 is not —CR—;
• wherein n is 0, 1, 2, or 3.