Structure–activity relationships study at the 3′-N position of paclitaxel. part 2: synthesis and biological evaluation of 3′-N-thiourea- and 3′-N-thiocarbamate-bearing paclitaxel analogues

The syntheses and preliminary biological evaluation of 3′-N-thiocarbamate- and 3′-N-thiourea-bearing paclitaxel analogues, 4a–f and 5a–e, are described. 3′-N-thiocarbamates 4a–e were found to be more potent than paclitaxel in both the tubulin polymerization assay and the in vitro cytotoxicity assay. Several derivatives of this class such as 4c, 4d, and 4e also exhibited some in vivo activity