Steroid-based head-to-tail amphiphiles as effective iono- and protonophores

The synthesis of five steroid-oligo(ethyleneglycol) conjugates () has been accomplished starting from commercially available epi-androsterone () and known 3β-[(tert-butyldiphenylsilyl)oxy]-5α-23,24-bisnorchol-16-en-6α,7β,22-triol (). The synthetic strategy was based on a convergent approach including stereoselective C-17 side chains construction and standard coupling reactions. The activities of the head-to-tail amphiphiles, once incorporated in 95:5 egg PC/PG vesicular membranes, have been assessed by direct determination of transported species by NMR techniques (23Na+) and fluorescence spectroscopy (H+). The sodium and proton transmembrane transport was compared to those evaluated for the polyene macrolide antibiotic amphotericin B and those shown by the known related C2-symmetric sterol-polyether conjugates and .