Fig. 1.

The geldanamycin (GA) derivative 17-DMAPG was synthesized with a yield of about 95%. The original yellow-orange color of GA turned purple upon derivatization to the C-17 position. This particular drug was chosen due to its favorable aqueous solubility (4.6 mg/ml) and amphiphilic properties. At physiologic pH, the tertiary amino group is un-protonated and 17-DMAPG easily crosses the lipid bilayer into the acidic compartment of liposomes and lipogels.