SYNTHESIS OF HELICALLY CHIRAL MOLECULES - STEREOSELECTIVE TOTAL SYNTHESIS OF THE PERYLENEQUINONES PHLEICHROME AND CALPHOSTIN-A

The total syntheses of the perylenequinone natural products phleichrome and calphostin A are detailed. The syntheses were based on (1) the de novo construction of regiospecifically oxygenated and selectively protected naphthalene subunits, (2) the enantiospecific introduction of the stereogenic side chains using a chiral (alpha-alkoxyalkyl)-lithium reagent, and (3) a highly atropdiastereoselective Cu(I)-promoted biaryl synthesis for the stereoselective introduction of the helical axis of the calphostins. The total syntheses were achieved in 13 or 14 steps, respectively, with excellent control of absolute stereochemistry.