TOTAL SYNTHESIS OF THE IONOPHORE ANTIBIOTIC CP-61,405 (ROUTIENNOCIN)

The total synthesis of the spiroketal ionophore antibiotic routiennocin 1 (CP-61,405) employing pi-allyltricarbonyl iron lactone complexes is described. These complexes were used as precursors for the preparation of substituted 2-phenylsulphonyl pyrans which, in turn, were coupled with iodoacetonides to afford spiroketals. Elaboration of the spiroketals by tetra-n-propylammonium perruthenate (TPAP) oxidation and coupling with 2-lithio-1-[beta(trimethylsilyl)ethoxymethyl] pyrrole followed by further oxidation, deprotection, oxidation and benzoxazole formation afforded the natural product. The preparation of the amino phenol fragment necessary for benzoxazole formation involved a novel amination procedure using benzeneselenenic anhydride and hexamethyldisilazane followed by samarium diiodide reduction.