A glycopeptide of the formula A1-A2-A3-A4-A5-A6-A7, in which each dash represents a covalent bond; wherein A1 comprises a modified or unmodified α-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 A2 to A7 comprises a modified or unmodified α-amino acid residue, whereby (i) A1 is linked to an amino group on A2, (ii) each of A2, A4 and A6 bears an aromatic side chain, which aromatic side chains are cross-linked together by two or more covalent bonds, and (iii) A7 bears a terminal carboxyl, ester, amide, or N-substituted amide group; and wherein one or more of A1 to A7 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+(R1)═CR2R3, N═PR1R2R3, N+R1R2R3 or P+R1R2R3 in which Y is a single bond, O, NR1 or S; X is O, NR1, S, SO2, C(O)O, C(O)S, C(S)O, C(S)S, C(NR1)O, C(O)NR1, 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.