Synthesis of Virgatol and Virgatenol, Two Naturally Occurring Coumarins from <i>Pterocaulon virgatum</i> (L.) DC, and 7-(2,3-Epoxy-3-methylbutoxy)-6-methoxycoumarin­, Isolated from <i>Conyza obscura</i> DCDemyttenaere, Jan; Vervisch, Stijn; Debenedetti, Silvia; Coussio, Jorge; Maes, Dominick; De Kimpe, Norbert · Synthesis · 2004