Intramolecular hydrogen abstraction reaction promoted by N-radicals in carbohydrates. Synthesis of chiral 7-oxa-2-azabicyclo[2.2.1]heptane and 8-oxa-6-azabicyclo[3.2.1]octane ring systems.
The reaction of phenyl and benzyl amidophosphates and alkyl and benzyl carbamate derivatives of aminoalditols with (diacetoxyiodo)benzene or iodosylbenzene and iodine is a mild and selective procedure for the synthesis of chiral 7-oxa-2-azabicyclo[2.2.1]heptane and 8-oxa-6-azabicyclo[3.2.1]octane ring systems under neutral conditions. This reaction can be considered to be an intramolecular N-glycosidation that goes through an intramolecular 1,5-hydrogen abstraction promoted by an N-amido radical followed by oxidation of the transient C-radical intermediate to an oxycarbenium ion. This methodology proved to be useful not only as a suitable strategy for the preparation of these bicyclic arrays but also for the selective oxidation of specific carbons of the carbohydrate skeleton, constituting a good procedure for the synthesis of protected N,O-uloses.
Francisco
Cosme G
CG
Instituto de Productos Naturales y Agrobiología del C.S.I.C., Carretera de La Esperanza 3, 38206 La Laguna, Tenerife, Spain.
Herrera
Antonio J
AJ
Suárez
Ernesto
E
D002241:Carbohydrates / Q000138:chemical synthesis / Q000737:chemistry*; D006536:Heptanes / Q000138:chemical synthesis* / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D007202:Indicators and Reagents; D008958:Models, Molecular; D015394:Molecular Structure; D009795:Octanes / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D013237:Stereoisomerism
D002241:Carbohydrates; D006536:Heptanes; D007202:Indicators and Reagents; D009795:Octanes; D006859:Hydrogen