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Polymerization of optical isomers of phenylalanine N ‐carboxyanhydride by various secondary amines
Author(s) -
Hashimoto Yutaka,
Aoyama Akimasa,
Imanishi Yukio,
Higashimura Toshinobu
Publication year - 1976
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.1976.360151208
Subject(s) - chemistry , polymerization , stereoselectivity , phenylalanine , steric effects , monomer , amine gas treating , polymer chemistry , polymer , nucleophile , organic chemistry , amino acid , catalysis , biochemistry
In the polymerization of phenylalanine NCA initiated by some secondary amines, the two enatimorphs of phenylalanine NCA were polymerized with the same rate, which was almost twice as high, as that found for the racemic mixture. This stereoselectivity was observed only when the polymerization was initiated by secondary amines which are sterically crowded and reluctant to undergo a nucleophilic addition to NCA. Poly( DL ‐phenylalanine) produced in the stereoselective polymerization had a higher molecular weight than that produced in nonstereoselective polymerization. These findings point to the possibility that the stereoselectivity arises only in those polymerizations which are propagated by the activated monomers and not in the propagation involving the terminal amine of the growing polymer. A possible mechanism for the stereoselective polymerization is proposed and examined.