Synthesis and biological evaluation of (-)-16-normethyldictyostatin: a potent analogue of (-)-dictyostatin.

[structure: see text] (-)-16-Normethyldictyostatin has been made by total synthesis and is a potent antitumor agent in cells expressing wild-type tubulin and in one mutant cell line that is resistant to paclitaxel, but it is much less active than dictyostatin in another paclitaxel-resistant cell line where Val is substituted for Phe270. This provides strong evidence that the C16 methyl group of the dictyostatins is oriented toward Phe270 in the paclitaxel-binding site on beta-tubulin.