Design, synthesis, and biological evaluation of EF- and ABEF- analogues of (+)-spongistatin 1.

The design, synthesis, and biological evaluation of two potential (+)-spongistatin 1 analogues have been achieved. The analogues, incorporating tethers (red) in place of the ABCD and the CD components of the (+)-spongistatin 1 macrolide, were designed such that the conformations of the retained skeleton (blue) would mimic the assigned major solution conformation of the natural product The nanomolar cytotoxicity observed for the ABEF analogue provides strong support for the assigned solution conformation.