title: Oxidative spirocyclisation routes towards the sawaranospirolides. Synthesis of ent-sawaranospirolides C and D.
abstract: Two routes are described for the synthesis of the sawaranospirolides, stereoisomeric spirolactone ascorbigenins isolated from Chamaecyparis pisifera. Trapping of the keto enal formed by oxidation of a functionalised 2-(4-hydroxybutyl)furan affords a potential butenolide spiroacetal precursor to sawaranospirolides A and C. Alternatively, epoxidation of protected 3-(dihydropyran-2-yl)-3-arylpropanoic acids results in spirolactonisation to generate ent-sawaranospirolide C; a related acid-mediated spirocyclisation gave access to ent-sawaranospirolide D.
authors.affiliation: Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, UKOX1 3TA. jeremy.robertson@chem.ox.ac.uk
authors.forename: Jeremy
authors.initials: J
authors.lastname: Robertson
authors.forename: Praful T
authors.initials: PT
authors.lastname: Chovatia
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Fowler
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Withey
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Woollaston
mesh_terms: D029780:Chamaecyparis / Q000737:chemistry*; D003500:Cyclization; D010084:Oxidation-Reduction; D013141:Spiro Compounds / Q000138:chemical synthesis*; D013237:Stereoisomerism
chemical_list: D013141:Spiro Compounds; C429215:spirolide A; C429216:spirolide C; C467769:spirolide D