title: A serendipitous synthesis of (+)-gregatin B, second structure revisions of the aspertetronins, gregatins, and graminin A, structure revision of the penicilliols.
abstract: A (DHQN)(2)AQN-promoted asymmetric dihydroxylation (92% ee) of the allyl chloride derived from enynol (E)-13 and an 8-step sequence provided access to the hydroxyethylated furanone (R)-21. Oxidation with MnO(2) furnished 50% furanone (+)-(R)-2a and 2.7% isomeric furanone (+)-(R)-3a. (R)-2a possesses the accepted constitution of (+)-gregatin B but its spectra are different. Surprisingly, (+)-(R)-3a equals the natural product. Analogous structure reassignments are due for the gregatins A and C-E, the aspertetronins A-B, graminin A, and the penicilliols A and B.
authors.affiliation: Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität Freiburg, Freiburg im Breisgau, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Burghart-Stoll
authors.forename: Reinhard
authors.initials: R
authors.lastname: Brückner
mesh_terms: D000498:Allyl Compounds / Q000737:chemistry; D003500:Cyclization; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D007783:Lactones / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000498:Allyl Compounds; D005663:Furans; D007783:Lactones; C559559:gregatin B; C540736:penicilliol A; C540735:penicilliol B; C559558:graminin A; C023698:allyl chloride