title: Facile synthesis of the tricyclic core of sarain A. 3-Oxidopyridinium betaine cycloaddition approach.
abstract: [formula: see text] A new approach to a suitably functionalized tricyclic core of sarains has been developed by means of Katritzky's cycloaddition using 3-oxidopyridinium betaines. A key step was the regioselective differentiation of the two nearly identical hydroxy groups derived from oxidative cleavage of the double bond in 8 to afford 14. A stereocontrolled construction of the tricyclic core 20 of sarains containing the requisite side chain at C-3' was achieved by an intramolecular conjugate addition.
authors.affiliation: Department of Chemistry, University of Alabama, Tuscaloosa 35487, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Sung
authors.forename: H I
authors.initials: HI
authors.lastname: Lee
authors.forename: Y
authors.initials: Y
authors.lastname: Chong
authors.forename: J K
authors.initials: JK
authors.lastname: Cha
mesh_terms: D000818:Animals; D001622:Betaine / Q000737:chemistry; D001952:Bridged-Ring Compounds / Q000138:chemical synthesis*; D003500:Cyclization; D010084:Oxidation-Reduction; D011161:Porifera / Q000737:chemistry; D011726:Pyridinium Compounds / Q000737:chemistry
chemical_list: C410432:3-oxidopyridinium betaine; D001952:Bridged-Ring Compounds; D011726:Pyridinium Compounds; C410431:sarain A; D001622:Betaine