4-(3-Fluoro-phen-yl)-1-(2-oxoindolin-3-yl-idene)thio-semicarbazide

Crystal structure of (Z)-2-(1-benzyl-2-oxoindolin-3-yl-idene)-N-phenyl-hydra-zine-1-carbo-thio-amide

The title compound, C₂₂H₁₈N₄OS, crystallized with four independent mol­ecules (A, B, C and D) in the asymmetric unit. All four mol­ecules have a Z conformation about the C=N bond with the benzyl ring being inclined to the indoline ring mean planes by 73.4 (2), 77.9 (2), 73.2 (2) and 77.2 (2)° in mol­ecules A, B, C and D, respectively. In mol­ecules A and B, the phenyl ring is inclined to the mean plane of the indoline ring mean plane by 12.0 (2) and 12.2 (2)°, respectively. However, in mol­ecules C and D, the same dihedral angles are larger, viz. 37.3 (2) and 36.4 (2)°, respectively. Consequently, the benzyl and phenyl rings are almost normal to one another in mol­ecules A and B [dihedral angles = 80.3 (3) and 87.1 (3)°, respectively], while in mol­ecules C and D, the same dihedral angles are only 48.8 (2) and 43.8 (3)°, respectively. There is an intra­molecular N—H⋯O hydrogen bond in each mol­ecule with an S(6) ring motif. There are also short intra­molecular N—H⋯N and C—H⋯S contacts in each mol­ecule. In the crystal, mol­ecules are linked via C—H⋯S hydrogen bonds and C—H⋯π inter­actions, forming a three-dimensional structure. The crystal was refined as a non-merohedral twin with a final BASF value of 0.110 (1).

Synthesis and structure-activity evaluation of isatin-β-thiosemicarbazones with improved selective activity toward multidrug-resistant cells expressing P-glycoprotein

Cancer multidrug resistance (MDR) mediated by ATP-binding cassette (ABC) transporters presents a significant unresolved clinical challenge. One strategy to resolve MDR is to develop compounds that selectively kill cells overexpressing the efflux transporter P-glycoprotein (MDR1, P-gp, ABCB1). We have previously reported structure-activity studies based around the lead compound NSC73306 (1, 1-isatin-4-(4'-methoxyphenyl)-3-thiosemicarbazone, 4.3-fold selective). Here we sought to extend this work on MDR1-selective analogues by establishing whether 1 showed "robust" activity against a range of cell lines expressing P-gp. We further aimed to synthesize and test analogues with varied substitution at the N4-position, and substitution around the N4-phenyl ring of isatin-β-thiosemicarbazones (IBTs), to identify compounds with increased MDR1-selectivity. Compound 1 demonstrated MDR1-selectivity against all P-gp-expressing cell lines examined. This selectivity was reversed by inhibitors of P-gp ATPase activity. Structural variation at the 4'-phenyl position of 1 yielded compounds of greater MDR1-selectivity. Two of these analogues, 1-isatin-4-(4'-nitrophenyl)-3-thiosemicarbazone (22, 8.3-fold selective) and 1-isatin-4-(4'-tert-butyl phenyl)-3-thiosemicarbazone (32, 14.8-fold selective), were selected for further testing and were found to retain the activity profile of 1. These compounds are the most active IBTs identified to date.