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

6 pages, 2 tables, 3 schemes.-- PMID: 12558429 [PubMed].-- Printed version published Feb 7, 2003.Supporting information available at: http://pubs.acs.org/doi/suppl/10.1021/jo026314hThe 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.This work was supported by the Investigation Programs no. BQU2000-0650 and BQU2001-1665 of the Dirección General de Investigación Científica y Técnica, Spain. A.J.H. thanks the Ministerio de Educación y Ciencia, Spain for fellowships