Functionalised bicyclic exo-glycals are readily obtained by base-catalysed (typically MeONa in MeOH) alkynol cycloisomerisation of ethynylated cyclic saccharides. Thus, base treatment of the phenylethynyl- and halogenoethynylated 1-O-acetyl-ribofuranoses 22–24 and the 4-ethynylated 1-thioglucopyranosides 30–33 gave – after deacetylation – selectively the (Z)-configured exocyclic enol ethers 26–28 (84–91%)