title: Alternative spiroketalization methods toward purpuromycin: a diketone approach to prevent benzofuran formation.
abstract: The central portion of purpuromycin has been assembled via a classical spiroketalization reaction. Key to promoting this reaction mode versus benzofuran formation was the oxidation state of the spiroketal core. With a higher oxidation state, even the electron-deficient isocoumarin found in purpuromycin could be employed directly in the spiroketalization. The two halves of the spiroketalization precursor were joined via a nitrile oxide/styrene 1,3-dipolar cycloaddition. A very mild selenium dioxide oxidation was used to introduce the required oxidation state of the spiroketal core.
authors.affiliation: Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA.
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Lowell
authors.forename: Michael W
authors.initials: MW
authors.lastname: Fennie
authors.forename: Marisa C
authors.initials: MC
authors.lastname: Kozlowski
mesh_terms: D001572:Benzofurans / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D009285:Naphthoquinones / Q000138:chemical synthesis / Q000737:chemistry; D010084:Oxidation-Reduction; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D001572:Benzofurans; D005663:Furans; D007659:Ketones; D009285:Naphthoquinones; D013141:Spiro Compounds; C520774:spiroketal; C009115:purpuromycin; C105430:benzofuran