2-​Azetidinecarboxylic acid, 1-​[5-​[[2-​amino-​5-​O-​(aminocarbonyl)​-​2-​deoxy-​L-​xylonoyl]​amino]​-​1,​5-​dideoxy-​1-​[3,​4-​dihydro-​5-​(hydroxymethyl)​-​2,​4-​dioxo-​1(2H)​-​pyrimidinyl]​-​β-​D-​allofuranuronoyl]​-​3-​ethylidene-​, (2S,​3Z)​-