Biohybrid peptidoglycan oligomers

A compound of formula Ia and/or formula Ib:

• wherein:
• R1 represents C1 to C20 alkyl or —CH2CH(CO2H)OC1-20 alkyl;
• R2 and R3 each independently represent —C(═O)R7;
• R4 to R6 each represent H;
• each R7 independently represents C1 to C20 alkyl;
• X1 and X2 independently represent -AA1-AA2-AA3-D-Ala-AA4, where:
• AA1 is selected from L-Ala, L-Gly, D-Gly or L-Ser;
• AA2 is selected from D-isoglutamate (γ-D-glutamate, γ-D-Glu), D-isoglutamine, or threo-3-hydroxyglutamate;
• AA3 is selected from L-homoserine, D-homoserine, D-5-hydroxylysine, D-Orn, L-Lys, D-Lys, L-Orn, L-2,4-diaminobutyrate, or L-5-hydroxylysine, where the amino group is functionalised to become a NHR8 group and/or, where present, the hydroxyl group is functionalised to become a OR8 group;
• and
• AA4 is selected from D-Ala, D-Ser or D-Lacate (D-Lac),
• at each occurrence R8 is independently selected from one or more of H, a fluorescent group or a pharmaceutically active moiety,
• n and m, and n′ and m′ are alternating repeating units, where n is from 5 to 100 and m is from 4 to 100, provided that m has the same value as n or is n−1 and n′ is from 5 to 100 and m′ is from 4 to 100, provided that m′ has the same value as n′ or is n′−1,
• p or p′ are 1 or 0, or
• a pharmaceutically acceptable salt, solvate or prodrug thereof.