Hydrolysable polymeric FMOC-linker

1. A process for the preparation of a compound of formula (2)

said process comprising the step of subjecting a compound of formula:

and an intermediate compound having a formula

to a coupling reaction to form the compound of formula (2),

wherein

PSA is polysialic acid;

R 1 is at each occurrence independently a (C 1 -C 8 )-alkyl;

R 2 is independently selected from the group consisting of —C(O)NR—, —C(O)NR—(C 1 -C 8 )-alkyl-NR—, —NRC(O)— and —NRC(O)—(C 1 -C 8 )-alkyl-NR,

R is independently either hydrogen or (C 1 -C 8 )-alkyl;

X is —SO 3 —R 3 ;

R 3 is independently selected from the group consisting of hydrogen, (C 1 -C 8 )-alkyl and (C 1 -C 8 )-alkyl-R 4 ;

R 4 is a polymer,

n is an integer selected from 0, 1, 2, 3, or 4; and

m is an integer selected from 1, 2, 3, or 4.

2. The process according to claim 1 , wherein R 2 is either —C(O)NR— or —NRC(O)— and wherein R is independently either hydrogen or C 1 -C 8 -alkyl.

3. The process according to claim 1 , further comprising reacting the compound of formula (2) and a protein or peptide drug to form a protein or peptide drug conjugate having the formula:

4. The process according to claim 3 , wherein the protein or peptide drug is selected from the group consisting of Factor VII, von Willebrand Factor (VWF), Factor VIIa, Factor VIII, and Factor IX.

5. The process according to claim 1 , wherein the PSA has a molecular weight of 5000 to 25000 Dalton.

6. The process according to claim 1 , wherein the PSA has a molecular weight of 5000 to 10000 Dalton.

7. The process according to claim 3 , wherein the PSA has a molecular weight of 5000 to 25000 Dalton.

8. The process according to claim 3 , wherein the PSA has a molecular weight of 5000 to 10000 Dalton.

9. The process according to claim 5 , wherein the PSA has a molecular weight of 5000 to 25000 Dalton.

10. The process according to claim 5 , wherein the PSA has a molecular weight of 5000 to 10000 Dalton.