Deprotonation reaction of alpha-amino acid N-carboxyanhydride at 4-CH position by yttrium tris[bis(trimethylsilyl)amide]

作者：Ling Jun^*; Peng Hui; Shen Zhiquan

来源：Journal of Polymer Science Part A: Polymer Chemistry , 2012, 50(18): 3743-3749.

DOI：10.1002/pola.26156

• block copolymer
• polypeptides
• ring-opening polymerization
• rare earth catalyst
• a-amino acid N-carboxyanhydride

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.

• 出版日期2012-9-15
• 单位浙江大学