(S)-4-Benzyloxazolidine-2,5-dione, can be used in the synthesis of amphiphilic anionic copolymer, methoxy poly(ethylene glycol)-b-poly(l-glutamic acid-co-l-phenylalanine) (mPEG-b-P(Glu-co-Phe)), used as an efficient drug delivery system for an anticancer drug doxorubicin hydrochloride (DOX·HCl).