Fig. 5.

Completion of the syntheses and cell growth inhibition data. a Four steps couple the ABCD* and EF fragments and produce the spongistatin 1 analogs 5a–c. b Cell growth inhibition assays with four human cancer cell lines establish that the D-ring modified analog 5a is approximately equipotent with spongistatin 1, while 5c represents a proof-of-concept result that the C(15) acetate may be structurally modified with only a minimal reduction in potency. LiHMDS lithium hexamethyldisilazide, HMPA hexamethylphosphoramide