title: Towards the total synthesis of calyculin C: preparation of the C(9)-C(25) spiroketal-dipropionate unit.
abstract: An asymmetric synthesis of the C(9)-C(25) spiroketal fragment of calyculin C is described. Key steps include two crotylation reactions using successively Brown's reagent and (Z)-crotyltrifluorosilane for the formation of the anti, anti, anti stereotetrad, ynone formation by a Pd-catalyzed coupling of a thiol ester with a terminal alkyne and a double intramolecular hetero-Michael addition for the stereoselective construction of the spiroketal framework.
authors.affiliation: Laboratory of Organic Chemistry, Department of Chemistry, Aalto University, School of Science and Technology, PO Box 16100, Kemistintie 1, FI-00076, Aalto, Finland.
authors.forename: Damien
authors.initials: D
authors.lastname: Habrant
authors.forename: Ari M P
authors.initials: AM
authors.lastname: Koskinen
mesh_terms: D000818:Animals; D002384:Catalysis; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D008387:Marine Toxins; D015394:Molecular Structure; D010080:Oxazoles / Q000138:chemical synthesis* / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D011161:Porifera / Q000737:chemistry*; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D005663:Furans; D008387:Marine Toxins; D010080:Oxazoles; D013141:Spiro Compounds; C549553:calyculin C; C520774:spiroketal; D010165:Palladium