C55-PP-GlcNAc GLCNAC-PP-LIPID GlcNAc-pyrophosphorylundecaprenol N-acetyl-glucosaminyl-pyrophosphorylundecaprenol lipid I undecaprenyl-N-acetyl-D-glucosaminyl-pyrophosphate undecaprenyl-N-acetyl-alpha-D-glucosaminyl-pyrophosphate