A glycopeptide of the formula A.sub.1-A.sub.2-A.sub.3-A.sub.4-A.sub.5-A.sub.6-A.sub.7, in which each dash represents a covalent bond; wherein A.sub.1 comprises a modified or unmodified .alpha.-amino acid residue, alkyl, aryl, aralkyl, alkanoyl, aroyl, aralkanoyl, heterocyclic, heterocyclic-carbonyl, heterocyclic-alkyl, heterocyclic-alkyl-carbonyl, alkylsulfonyl, arylsulfonyl, guanidinyl, carbamoyl, or xanthyl; wherein each of A.sub.2 to A.sub.7 comprises a modified or unmodified .alpha.-amino acid residue, whereby (i) A.sub.1 is linked to an amino group on A.sub.2, (ii) each of A.sub.2, A.sub.4 and A.sub.6 bears an aromatic side chain, which aromatic side chains are cross-linked together by two or more covalent bonds, and (iii) A.sub.7 bears a terminal carboxyl, ester, amide, or N-substituted amide group; and wherein one or more of A.sub.1 to A.sub.7 is linked via a glycosidic bond to one or more glycosidic groups each having one or more sugar residues, at least one of the sugar residues bearing one or more substituents of the formula YXR, N.sup.+(R.sub.1)=CR.sub.2R.sub.3, N=PR.sub.1R.sub.2R.sub.3, N.sup.+R.sub.1R.sub.2R.sub.3 or P.sup.+R.sub.1R.sub.2R.sub.3 in which Y is a single bond, O, NR, or S; X is O, NR.sub.1, S, SO.sub.2, C(O)O, C(O)S, C(S)O, C(S)S, C(NR.sub.1)O, C(O)NR.sub.1, or halo (in which case Y and R are absent). A chemical library comprising a plurality of the glycopeptides of the invention.A method for preparing a glycopeptide by glycosylation of an aglycone derived from a glycopeptide antibiotic.A method for preparing a glycopeptide by preparing a pseudoaglycone from a glycopeptide antibiotic and glycosylating the pseudoaglycone.