Journal
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
Volume 50, Issue 18, Pages 3743-3749Publisher
WILEY-BLACKWELL
DOI: 10.1002/pola.26156
Keywords
block copolymer; polypeptides; ring-opening polymerization; rare earth catalyst; a-amino acid N-carboxyanhydride
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Funding
- National Natural Science Foundation of China [21174122]
- Special Funds for Major Basic Research Projects [G2011CB606001]
- Zhejiang Provincial Natural Science Foundation of China [Y4110115]
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Reaction of yttrium tris[bis(trimethylsilyl)amide] [(TMSN)3Y] with equivalent L-alanine N-carboxyanhydride (ALA NCA) yields yttrium a-isocyanato carboxylate (II), yttrium ketenyl carbamate (III), and hexamethyldisilazane (V). The products indicate that 4-CH group of ALA NCA monomer is deprotonated in addition to 3-NH group, which has been neglected in NCA chemistry for decades. This result proves the acidity of 4-CH in NCA and provides the first direct evidence for racemization phenomenon of NCA in strong base in microscopic aspect. Rare earth tris[bis(trimethylsilyl)amide] (TMSN)3Ln (Ln = Sc, Y, La, Dy, and Lu) compounds are high efficient catalysts for ring-opening polymerizations of NCAs. Polypeptides can be produced in quantitative yields with narrow molecular weight distributions below 1.3, and block copolypeptides can be facilely prepared by sequential addition method. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
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