Intramolecular 1,8-hydrogen-atom transfer reactions in (1 -> 4)-o-disaccharide systems: conformational and stereochemical requirements

C.G. Francisco, A.J. Herrera, A.R. Kennedy, A. Martin, D. Melian, I. Perez-Martin, L.M. Quintanal, E. Suarez

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Abstract

The stereochemical and conformational factors controlling the intramolecular hydrogen-atom transfer (HAT) reaction between the two pyranose units in a (14)-O-disaccharide when promoted by a primary 6-O-yl radical are studied. Models with -D-Glcp-(14)--D-Glcp, -L-Rhamp-(14)--D-Galp or -D-Manp-(14)--L-Gulp skeletons led exclusively to the abstraction of the hydrogen from HC-5 and the formation, through a nine-membered transition state, of a 1,3,5-trioxocane ring system in a stable boat-chair conformation. Notwithstanding, derivatives of -L-Rhamp-(14)--D-Glcp or -D-Manp-(14)--D-Galp exclusively abstract the hydrogen from HC-1 through a seven-membered transition state and, therefore, lead to an interglycosidic spiro ortho ester.
Original languageEnglish
Pages (from-to)10369-10381
Number of pages12
JournalChemistry - A European Journal
Volume14
Issue number33
DOIs
Publication statusPublished - 2008

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Keywords

  • carbohydrates
  • disaccharides
  • esters
  • radical reactions
  • trioxocane

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