Bicyclic diazasugars. Part 3: β-d-Mannose and 6-deoxy-β-l-gulose analogues

A bicyclic analogue of β-d-mannopyranose with nitrogen atoms replacing the ring and glycosidic oxygen atoms has been prepared in a single step from 5-O-mesyl-d-mannofuranose by a process that likely involves double displacement and an epoxide intermediate. A similar but protected bicyclic analogue of 6-deoxy-β-l-gulopyranose has been prepared by an electrophilic cyclization reaction.