Abstract: A compound of formula (I) and pharmaceutical acceptable salts, solvates, stereoisomers and prodrugs thereof, in isolation or in mixture, wherein, independently at each occurrence: R1 and R2 are selected from hydrogen, oxygen so as to form nitro or oxime, amino, sulfate, and sulfonic acid, and organic groups having 1-30 carbons and optionally containing 1-6 heteroatoms selected from nitrogen, oxygen, phosphorous, silicon, and sulfur, where R1 and R2 may, together with the N to which they are both bonded, form a heterocyclic structure that may be part of an organic group having 1-30 carbons and optionally containing 1-6 heteroatoms selected from nitrogen, oxygen and silicon, and where R1 may be a 2, or 3 atom chain to numeral 2 so that —N—R1— forms part of a fused bicyclic structure to ring A; R3 and R4 are selected from direct bonds to 6 and 7 respectively so as to form carbonyl groups, hydrogen, or a protecting group such that R3 and/or R4 is part of hydroxyl or carbonyl protecting group; nu