title: Carboxybenzyl group as an o-nucleophile in the C-H allylic oxidation: total synthesis of (-)-castanospermine.
abstract: The first palladium-mediated C-H allylic oxidation with a Cbz group acting as an O-nucleophile is reported. It was found that this transformation is promoted by rare-earth metal triflates: Yb(OTf)(3) or Sc(OTf)(3). A possible catalytic cycle is proposed. This reaction was applied in the synthesis of a d-xylose derived oxazolidinon, a versatile intermediate used further in the stereoselective synthesis of unnatural (-)-castanospermine. Cyclization of the key intermediate with PhSeBr afforded the desired bicyclic scaffold. In an alternative route, hydroboration/oxidation followed by DPPA-mediated cyclization was used.
authors.affiliation: Institute of Organic Chemistry, Polish Academy of Sciences , Kasprzaka 44/52, 01-224 Warsaw, Poland.
authors.forename: Michał
authors.initials: M
authors.lastname: Malik
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Witkowski
authors.forename: Sławomir
authors.initials: S
authors.lastname: Jarosz
mesh_terms: D001386:Azides / Q000737:chemistry; D002384:Catalysis; D003500:Cyclization; D007212:Indolizines / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D010165:Palladium; D013237:Stereoisomerism; D014994:Xylose / Q000138:chemical synthesis / Q000737:chemistry*; D054836:Indolizidines
chemical_list: D001386:Azides; D007212:Indolizines; D010165:Palladium; D014994:Xylose; C007523:diphenylphosphorazidate; C037806:castanospermine; D054836:Indolizidines