173778-30-8Relevant articles and documents
Chemistry of 1-alkoxy-1-glycosyl radicals: The manno- and rhamnopyranosyl series. Inversion of α- to β-pyranosides and the fragmentation of anomeric radicals
Crich, David,Sun, Sanxing,Brunckova, Jarmila
, p. 605 - 615 (1996)
The formation and stereoselective quenching of 1-mannopyranosyl radicals by a tributyltin hydride-mediated intramolecular 1,5-hydrogen abstraction sequence is described. A competing process is 1,4-hydrogen atom abstraction leading principally to glucopyran-2-ulosides. Fragmentation of the anomeric radical resulting in the formation of ring opened products is a problem in certain series. The chemistry is dictated to a considerable extent by the nature of the protecting groups employed with the 4,6-benzylidene series and, for rhamnose, the Ley 3,4-dispiroketal, being particularly susceptible to the 1,4-hydrogen atom abstraction but less to the fragmentation. Photochemical conditions are described, in which these side reactions are practically eliminated, and applied to the inversion of an α- to a β-mannoside in a disaccharide.