丁二酸酐 、
1,5-bisbutyl (2S)-2-aminopentanedioate 、 2-azidoethyl β-N-acetyl-galactosamine 以49%的产率得到(S)-2-{3-[2-((2R,3R,4R,5R,6R)-3-Acetylamino-4,5-dihydroxy-6-hydroxymethyl-tetrahydro-pyran-2-yloxy)-ethylcarbamoyl]-propionylamino}-pentanedioic acid dibutyl ester