The synthesis of fused furanosyl β-amino esters from protected sugar lactones is described, using the combination of a Wittig type reaction and 1,4-addition of benzylamine on the resulting glycosylidenes. This sequence of reactions afford either N-glycosyl-3-ulosonic acid esters, which are the β-analogues of anomeric sugar α-amino esters, or open-chain sugar β-enamino esters, when a retro-Michael reaction