title: L-Phe end-capped poly(L-lactide) as macroinitiator for the synthesis of poly(L-lactide)-B-poly(L-lysine) block copolymer.
abstract: A poly(L-lactide)-b-poly(Nepsilon-(Z)-L-lysine) (PLLA-b-PZLys) block copolymer was synthesized through the ring-opening polymerization of Nepsilon-(Z)-lysine-N-carboxyanhydride using L-Phe-terminated PLLA as a macroinitiator. The L-Phe-terminated PLLA was prepared through a novel three-step process. First, the hydroxyl-terminated PLLA was synthesized through the ring-opening polymerization of L-lactide initiated by n-butanol under the existence of tin(II) ethylhexanoate. Subsequently, the complete capping of the hydroxyl end group of PLLA with BOC-L-Phe was achieved by using a mixed anhydride of BOC-L-Phe under the catalysis of 4-(1-pyrrolidinyl) pyridine. Finally, the free amino end group was obtained by removal of the t-butoxycarbonyl group through trifluoroacetic acid treatment under anhydrous condition. All these treatments were conducted under mild conditions, thus avoiding the breakdown of the PLLA backbone. Poly(L-lactide)-b-poly(L-lysine) block copolymer was produced after deprotection treatment of PLLA-b-PZLys. The structure of the block copolymer was confirmed by 1H NMR, IR, and GPC. Adjustment of the ratio of the NCA monomer to the macroinitiator could control the chain length of the PLys block.
authors.affiliation: Biomaterials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Yujiang
authors.initials: Y
authors.lastname: Fan
authors.forename: Guoping
authors.initials: G
authors.lastname: Chen
authors.forename: Junzo
authors.initials: J
authors.lastname: Tanaka
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tateishi
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry; D002208:Caproates / Q000737:chemistry; D002384:Catalysis; D008239:Lysine / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008422:Materials Testing; D008956:Models, Chemical; D008970:Molecular Weight; D010649:Phenylalanine / Q000737:chemistry*; D011091:Polyesters / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013696:Temperature; D014269:Trifluoroacetic Acid / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D002208:Caproates; D046911:Macromolecular Substances; D011091:Polyesters; D011108:Polymers; D011725:Pyridines; C037652:hexanoic acid; C033616:poly(lactide); D010649:Phenylalanine; D014269:Trifluoroacetic Acid; D008239:Lysine; C023666:pyridine