Glycosylated glycopeptides

Gylcosylated glycopeptide antibiotics having the formula I in which A is the remaining portion of a glycopeptide antibiotic of the vancomycin/ristocetin class or a chemical derivative thereof, and O is the phenolic oxygen of the central (B) ring of the triaryl ether region of the glycopeptide antibiotic; and R is a monosaccharide or disaccharide or a deoxy or amino variant thereof; provided that R is not the natural sugar species attached at this site on the glycopeptide core, and R is not glucosyl when A is the remaining portion of vancomycin, A51568A, M43D, or A51568B and their salts are useful new antibiotics. A process for producing compounds of formula (I) or a chemical derivative thereof, or a pharmaceutically acceptable salt thereof. These derivatives are useful for treating or preventing infection in an animal by gram-positive bacteria and also increase feed-utilization efficiency, promote growth in domestic animals and increase propionate production in lactating ruminants.