Lysine glycopeptides

The connective-tissue components collagen and elastin are the probable source of some urinary protein-carbohydrate compounds. A glycopeptide containing approximately equimolar proportions of hy-droxy-L-lysine, D-glucose, and D-galactose has been isolated from... 

FIGURE 44-2 Action of fi-iactam antibiotics in SUqyhytococcus aureus. The bacterial cell wall consists of glycopeptide polymers linked via bridges between amino acid side chains. In S. aureus, the bridge is (Gly),-D-Ala between lysines. The cross-linking is catalyzed by a transpeptidase, the enzyme that penicillins and cephalosporins inhibit. 

Experiments were conducted to determine the free amino groups available for reaction with dansyl chloride. Only one faint fluorescent area in the region of dansyl-lysine was observed. No dansyl-ethanolamine was observed. However, if the pol3nner was first treated with 6 N HCl to hydrolyze the amino acids, dansyl amino acids were obtained. Quantitative analysis for ethanolamine from the amino acid analyzer gave 1.3 ethanolamine residues for 2 proline residues. The low solubility of the polymer in aqueous solution may have been the primary factor leading to lack of derivatization of the intact glycopeptide. 

For the synthesis of glycopeptides from Boc/Fmoc-protected amino adds, the initial carboxylic acid activation step was performed by milling at lower fieqnency of 450rpm to avoid deprotection (Scheme 3.38). Ball milling of amine 137 with amino-protected lysine 136 formed the corresponding amide 138 and urea 139 in good overall yield. 

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