Heterotelechelic poly(ethylene glycol)s are widely used in the modification, conjugation, and crosslinking of biomacromolecules. A series of heterotelechelic PEGs with amino acid at one end and hydroxyl group at another end, including alpha-glycine-omega-hydroxyl-PEG, alpha-proline-omega-hydroxyl-PEG, and alpha-phenylalanine-omega-hydroxyl-PEG, were first synthesized in this study. The reaction proceeded at ambient temperature under alkaline conditions via an aqueous solution polymerization of ethylene oxide. Amino group of glycine, proline, and phenylalanine was the initiating center in the polymerizations, and carboxyl group of these amino acids was reserved as one of the active end groups of the obtained heterotelechelic PEG. Purification of the desired products was accomplished by silica gel column chromatography. The obtained heterotelechelic PEGs were characterized by means of FT-IR, H-1 NMR, C-13 NMR, MS, and RP-HPLC. They were in different forms depending on the type of initiating amino acid, e.g. alpha-glycine-omega-hydroxyl-PEG and alpha-phenylalanine-omega-hydroxyl-PEG are in branched form, and alpha-proline-omega-hydroxyl-PEG is linear. Amino acids were conjugated to PEG chains through the stable carbon-nitrogen bond. Compared with the traditional critical polymerization conditions, the advantage of this method is that various amino acid ended heterotelechelic PEGs can be designed and obtained by using different amino acid as the initiator through a much more convenient route, which proceeded in aqueous solution at ambient temperature. (C) 2008 Wiley Periodicals, Inc.