Patent ID: 7714147

Claim:
A method of preparing a compound according to formula 1: wherein PG is a silyl protecting group and at least one of position 1, 2, 3, 4, 5, 6, 7 or 8 is bound to radical Y; Y is a radical containing a N-maleimidyl-moiety having a structure R 1 is a (C 1 -C 8 )-alkyl; R 2 is 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, wherein R is independently either hydrogen or C 1 -C 8 -alkyl; at least one of an available position 1, 2, 3, 4, 5, 6, 7 or 8 is optionally bound to radical X; 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 ; and R 4 is a polymer; said method comprises the steps of reacting the 9-hydroxymethyl group of a compound of formula 2: wherein at least one of position 1, 2, 3, 4, 5, 6, 7 or 8 is bound to an amine, with a silyl protecting reagent introducing PG, and subsequently reacting said compound with an N-maleimidyl reagent to form the compound of formula (1).