Polycyclic scaffolds from fructose

Iodocyclisation of polybenzylated allyl α-C-fructofuranoside 1 afforded the bicyclic iodoether 2 through debenzylation at C-1; treatment of 2 with zinc and acetic acid restored the allylic group with concomitant deprotection of the hydroxyl group at C-1, which was oxidised to the corresponding aldehyde 4. Reaction of 4 with vinylmagnesium bromide afforded diene 5, whose double bonds were reacted regioselectively in order to obtain, upon iodocyclisation under different experimental conditions, bicycles 6 or 7, or tricycle 8.