Branched monodispersed polyethylene glycol, intermediate and methods for producing same

A branched monodispersed polyethylene glycol represented by formula (1) wherein 90% or more of PEG compounds constituting the branched monodispersed PEG have the same number of repeating ethylene oxide units n:

• wherein, in the formula (1),
• X1 is a functional group that forms a covalent bond upon a reaction with a functional group present in a biofunctional molecule and is selected from the group consisting of an active ester group, an active carbonate group, an aldehyde group, an isocyanate group, an isothiocyanate group, an epoxy group, a maleimide group, a vinyl sulfone group, an acryl group, a sulfonyloxy group, a carboxy group, a thiol group, a dithiopyridyl group, an α-haloacetyl group, an alkynyl group, an allyl group, a vinyl group, an amino group, an oxyamino group, a hydrazide group and an azide group;
• n is an integer of 8 to 24, which represents number of repeating units of ethylene oxide units;
• and
• L1 represents a single bond, —NH—, -L2-(CH2)m1- or -L2-(CH2)m1-L3-(CH2)m2-, L2 represents an ether bond, an amide bond, an urethane bond or a single bond, L3 represents an ether bond, an amide bond or an urethane bond, and m1 and m2 represent each independently an integer of 1 to 5.