Method for producing multi-arm type polyethylene glycol derivative

A method for producing a multi-arm type polyethylene glycol derivative represented by the following formula (1), wherein the following step (A), step (B), step (C), step (D), and step (E) are carried out in this order:

• wherein, in the formula (1),
• L is a group selected from the group consisting of a linear or branched alkylene group having 3 to 8 carbon atoms, a substituted or unsubstituted arylene group having 6 to 12 carbon atoms and a cycloalkylene group having 6 to 12 carbon atoms,
• k represents 1 or 2,
• n represents an average molar number of oxyethylene groups added and n represents an integer between 3 and 600,
• X represents an alkylene group which may have a single bond, an ester bond, a urethane bond, an amide bond, an ether bond, a carbonate bond, a secondary amino group, a urea bond, a thioether bond, or a thioester bond in a chain or at a terminal, and
• Y represents a chemically reactive functional group;
• Step (A):
• a step of protecting an even number of hydroxyl groups, while leaving only the hydroxyl group at the 1-position of a polyhydric alcohol having an odd number of hydroxyl groups, other than the hydroxyl group at the 1-position by cyclic benzylidene acetalization,
• Step (B):
• a step of linking two molecules of the compound obtained in the step (A) to a compound represented by the following formula (2) by an etherification reaction to obtain a compound, and purifying the obtained compound by recrystallization in dimethylformamide:
• A-L-A (2)
• wherein, in the formula (2),
• L represents a group selected from the group consisting of a linear or branched alkylene group having 3 to 8 carbon atoms, a substituted or unsubstituted arylene group having 6 to 12 carbon atoms and a cycloalkylene group having 6 to 12 carbon atoms, and
• A represents a halogen atom selected from chlorine, bromine or iodine, or a sulfone-based leaving group,
• Step (C):
• a step of deprotecting the cyclic benzylidene acetal structure at the terminal of the compound obtained in the step (B), where 8 hydroxyl groups are formed in the case of k=1 and 12 hydroxyl groups are formed in the case of k=2,
• Step (D):
• a step of polymerizing 3 to 600 mol of ethylene oxide to each hydroxyl group of the compound obtained in the step (C) to obtain a multi-arm type polyethylene glycol derivative, and
• Step (E):
• a step of functionalizing the hydroxyl group at the terminal of the multi-arm type polyethylene glycol derivative obtained in the step (D).