Acceptable salt or solvate of the compound or a pharmaceutically thereof agent of formula I:
Formula I

Wherein
R ² is to have the formula III:
Formula III

Wherein, A is C _{5 -7} aryl group, X is , Or NHR, and ^N, wherein R ^N is selected from the group consisting of H and C _{1 -4} alkyl,
(i) and Q ¹ is a single bond, Q ² is a single bond and -Z- (CH _{2) n} - is selected from wherein Z is selected from a single bond, O, S and NH, n is from 1 to 3, or .; or
(ii) Q ¹ is a -CH = CH-, Q ² is a single bond;
R ¹² is OH, CO ₂ H, CO ₂ R a ^O, C _{5 -10} aryl group substituted by an element selected from, wherein R ^O is selected from C _{1 -4} alkyl;
R ⁶ and R ⁹ are independently H, R, OH, OR, SH, SR, NH 2, NHR, NRR ', is selected from nitro, Me ₃ Sn and halo;
Wherein, R and R 'is C _{1 -12} independently an optionally substituted alkyl, C _{3 -20} heterocyclyl, and C _{5 -20} are selected from aryl groups;
R ⁷ is H, R, OH, OR, SH, SR, NH 2, NHR, NHRR ', is selected from nitro, Me ₃ Sn and halo;
(a) and R ¹⁰ is H, R ¹¹ is OH or OR ^A (Wherein R ^A is C _{1 -4} alkyl), and; or
(b) R ¹⁰ and R ¹¹ is nitrogen they are attached between the nitrogen atom and the carbon atoms forming the carbon-carbon double bond or; or
(c) R ¹⁰ is H, R ¹¹ is SO M _z (where z is 2 or 3, M is acceptable cation being a monovalent pharmaceutically shown below);
R "is one or more heteroatoms in the chain, e.g. O, S, NR ^N2 (Where R ^N2 is selected from H or C _{1 -4} alkyl) and / or aromatic rings, e.g. benzene or pyridine is a C _3-12 alkylene group which may be disposed;
Y and Y 'is selected from O, S or NH;
^{R 6 ', R 7',} R 9 ' are each R ^6, R ⁷ and selected from the same group as R ^9, R ^10' and R ^{11 'are} the same as R ¹⁰ and R ^11, where R ¹¹ and R If ^{11 'is} SO _z M days, M may represent a divalent pharmaceutically acceptable cation in two.