A Survey of Synthetic Routes towards the Pyranonaphthoquinone Antibiotic Pentalongin and Syntheses of the Corresponding Nitrogen Derivatives - Claessens, Sven; Verniest, Guido; Jacobs, Jan; Van Hende, Eva; Habonimana, Pascal; Nguyen Van, Tuyen; Van Puyvelde, Luc; De Kimpe, Norbert; Van Puyvelde, Luc (Synlett, 2007)