Patent ID: 7888536

Claim:
A method for selectively making specific discrete (polyethylene glycol) (dPEG) compounds containing a discrete and predetermined number of ethylene oxide moieties, which comprises the steps of: (a) forming a reaction mixture comprising one or more of (i) a first dPEG reactant having the general structural formula I R 1 -dPEG x -OH I and a second dPEG reactant having the general structural formula II R 2 -dPEG y -OR 2 II or (ii) a first dPEG reactant having the general structural formula I′ R 1 -dPEG x -OR 2 I′ and a second dPEG reactant having the general structural formula II′ HO-dPEG y -OH II′ (b) adding a non-sodium hydride ionizing agent, which is potassium t-butoxide, to said reaction mixture in the presence of a catalyst and under reaction conditions to produce a dPEG compound having the general structural formula III R 1 -dPEG 2x+y -R 1 III wherein said ionizing compound is added to a reaction mixture of compounds I and II, or I′ and II′, at a rate that is about equal to the rate at which compound XXII or compound XXII′, respectively, reacts with compound II or II′, respectively, forming XXII or XXII′, respectively, in situ, wherein R 1 -dPEG x -O − M + XXII HO-dPEG y -O − M + XXII′ wherein dPEG represents a (OCH 2 CH 2 ) moiety, each R 1 independently is one or more of a removable hydroxyl protecting group (PG), where PG is removable under mild acid conditions and is stable to base, a protected functional group, or a functional group (FG); x ranges from about 1 to 300; R 2 is a leaving group, and y ranges from about 1 to 300.