title: Intramolecular 1,8-hydrogen atom transfer reactions in disaccharide systems containing furanose units.
abstract: A previously developed 1,8-hydrogen atom transfer (HAT) reaction promoted by 6-O-yl alkoxyl radicals between the two pyranose units in Hexp-(1→4)-Hexp disaccharides has been extended to other systems containing at least a furanose ring in their structures. In Penf-(1→3)-Penf (A) and Hexp-(1→3)-Penf (B) disaccharides, the 1,8-HAT reaction and concomitant cyclization to a 1,3,5-trioxocane ring are in competition with radical β-scission of the C4-C5 bond and formation of dehomologated products. The influence of the stereoelectronic β-oxygen effect on the β-scission and consequently on the 1,8-HAT reaction has been studied using the four possible isomeric d-furanoses. d-xylo- and d-lyxo-derivatives afforded preferentially 1,8-HAT products, whereas d-arabino- and d-ribo-derivatives gave exclusively direct β-scission of the alkoxyl radical. When the 6-O-yl radical is on a pyranose ring, as occurs in Penf-(1→4)-Hexp (C), it has been shown to provide the cyclized products exclusively.
authors.affiliation: Instituto de Productos Naturales y Agrobiología del CSIC, Carretera de La Esperanza 3, 38206 La Laguna, Tenerife, Spain.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Guyenne
authors.forename: Elisa I
authors.initials: EI
authors.lastname: León
authors.forename: Angeles
authors.initials: A
authors.lastname: Martín
authors.forename: Inés
authors.initials: I
authors.lastname: Pérez-Martín
authors.forename: Ernesto
authors.initials: E
authors.lastname: Suárez
mesh_terms: D003500:Cyclization; D004187:Disaccharides / Q000138:chemical synthesis* / Q000737:chemistry; D005663:Furans / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D004187:Disaccharides; D005663:Furans; D006859:Hydrogen