Patent ID: 7741319

Claim:
A compound of formula III: or a pharmaceutically acceptable salt thereof, wherein: R 6 and R 9 are independently selected from H, R, OH, OR, SH, SR, NH 2 , NHR, NRR′, nitro, Me 3 Sn and halo; R and R′ are independently selected from optionally substituted C 1-12 alkyl, C 3-20 heterocyclyl and C 5-20 aryl groups; the compound being a dimer with each monomer being of formula (III), where the R 8 of each monomer form together a dimer bridge having the formula —X—R″—X— linking the monomers, where R″ is a C 3-12 alkylene group, which chain may be interrupted by one or more heteroatoms and/or aromatic rings, and each X is independently selected from O, S, or NH, and R 7 is selected from H, R, OH, OR, SH, SR, NH 2 , NHR, NRR′, nitro, Me 3 Sn and halo, or any pair of adjacent groups from R 6 to R 9 together form a group —O—(CH 2 ) p —O—, where p is 1 or 2; either R 10 and R 16 together form a double bond between N10 and C11, or R 10 is H and R 16 is OH; R 15 is an optionally substituted C 5-20 aryl group, wherein the optional substituents are independently selected from the group consisting of C 1-12 alkyl, C 3-12 cycloalkyl, C 3-20 heterocyclyl, C 5-20 aryl, halo, hydroxyl, —OR 1 wherein R 1 is a C 1-7 alkyl group or C 3-20 heterocyclyl group or C 5-10 aryl group, alkoxy, —CH(OR 1 )(OR 2 ) wherein R 1 is as defined above and R 2 is independently a C 1-7 alkyl group or C 3-20 heterocyclyl group or C 5-10 aryl group or R 1 and R 2 together with the two oxygen atoms to which they are attached form a heterocyclic ring having from 4 to 8 ring atoms, —CH(OH)(OR 1 ) wherein R 1 is as defined above, ketal, hemiketal, oxo, thione, imino, formyl, acyl, carboxy, thiocarboxy, thiolocarboxy, —C(═NH)OH, —C(═NOH)OH, —C(═O)OR 1 wherein R 1 is as defined above, acyloxy, oxycarboyloxy, amino, amido, thioamido, acylamido, aminocarbonyloxy, ureido, guanidine, tetrazolyl, amindino, nitro, nitroso, azido, cyano, isocyano, cyanato, isocyanato, thiocyano, isothiocyano, sulfhydryl, thioether, disulfide, sulfine, sulfone, —S(═O)OH, —SO 2 H, —S(═O) 2 OH, —SO 3 H, sulfinate, sulfonate, sulfinyloxy, sulfonyloxy, sulfate, sulfamyl, sulfonamide, sulfamino, sulfonamino, sulfinamino, phosphino, phosphor, phosphinyl, phosphono, —P(═O)(OR 17 ) 2 wherein R 17 is —H or C 1-7 alkyl group or C 3-20 heterocyclyl group or C 5-20 aryl group, phosphonooxy, —PO(═O)(OR 17 ) 2 wherein R 17 is as defined above, —OP(OH) 2 , phosphate, phosphoramidite, and phosphoramidate; and wherein heteroatoms of the heterocyclyl groups and the optional heteroatoms of the alkylene groups are independently selected from the group consisting of N, S, and O.