Multivalent polymers, processes for their preparation, and their use for preparing biologically active compounds

A linear polypeptide comprising at least two structural elements of the formula

• wherein
• each A is independently a trivalent, aliphatic hydrocarbon radical having from 1 to 12 carbon atoms which is unsubstituted or substituted by one or more substituents selected from the group consisting of C1-C4-alkyl, C1-C4alkoxy, C1-C4alkylthio, benzyl and benzyloxy;
• each R1 is independently a direct bond or C1-C6alkylene;
• each X1 is independently —C(O)O—,—C(O)NR—, —NR—, —S— or —O—;
• each R2 is independently a bivalent bridging group;
• each X2 is independently O or NR;
• or
• independently, each R2 and X2 are together a direct bond;
• and
• each R is independently H or C1-C6alkyl;
• with the proviso that X1 is not —NR—, —S— or —O— when R1 is a direct bond;
• and
• each R3 is independently a biological active group which is covalently bound to the S atom either directly or by way of a bridging group Y, wherein at least one R3 is different from another R3.