Synthesis and Cytotoxicity Studies of Titanocene C Analogues

From the carbolithiation of 6-N,N-dimethylamino fulvene (3) and 2,4[bis(N,N-dimethylamino)methyl]-N-methylpyrrolyl lithium (2a), N-(N',N'-dimethylaminomethyl)benzimidazolyl lithium (2b), or p-(N,N-dimethylamino)methylphenyl lithium (2c), the corresponding lithium cyclopentadienide intermediate (4a-c) was formed. These three lithiated intermediates underwent a transmetallation reaction with TiCl(4') resulting in N,N-dimethylamino-functionalised titanocenes 5a-c. When these titanocenes were tested against a pig kidney epithelial cell line (LLC-PK), the IC50 values obtained were of 23, and 52 muM for titanocenes 5a and 5b, respectively. The most cytotoxic titanocene in this paper, 5c with an IC50 value of 13 muM, was found to be approximately two times less cytotoxic than its analogue Titanocene C (IC50=5.5 muM) and almost four times less cytotoxic than cisplatin, which showed an IC50 value of 3.3 muM when tested on the LLC-PK cell line.