Intramolecular 1,3-dipolar additions in 4-O-allyl pyranoside 6-nitrones: An approach to chiral pyrano-pyrans and pyrano-oxepans

Abstract Treatment of the easily prepared 6-aldehydo-glucopyranoside allyl ether (5) with N-benzylhydroxylarnine gave nitrone (6), which underwent a 1,3-dipolar addition to the 4-O-allyl group giving after deprotection and hydrogenolysis the chiral pyrano-pyran (11) and the pyrano-oxepan (13).