The major isomer, (E)-1,4-anhydro-1-ethoxy-carbonyl(formylamino)methylene-2,3 : 5,6-diO-isopropyl-idene-D-mannitol (2), obtained by the reaction of α-metallated ethyl isocyanoacetate with 2,3 :5,6-di-O-isopropylidene-D-mannono-1,4-lactone, gives on hydrogenation and acidic hydrolysis, 2-L-(and 2-D-)(β-D-mannofuranosyl)glycines (10) and (11), and can be converted into 2-L- and 2-D-(β-D-lyxofuransyl)glycines (12) and (13).