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Polymerization of amino acid derivatives by polymer catalysts. V. Polymerization of DL‐β‐phenylalanine N‐carboxyanhydride by several poly(N‐alkylamino acid) diethylamides

The polymerization of DL‐β‐phenylalanine N‐carboxyanhydride (NCA) initiated by poly(N‐benzylglycine)diethylamide (DEA) and poly(N‐methyl‐DL‐alanine)DEA has been investigated. As previously reported, polysarcosine DEA, poly‐N‐ethylglycine DEA, and poly‐N‐n‐propylglycine DEA showed marked accelerations in the polymerization of DL‐β‐phenylalanine NCA as compared with the polymerization initiated by low molecular weight, amines having similar base strength. However, this phenomenon (the chain effect) was not observed with the two polymer catalysts studied in the present investigation With poly‐N‐methyl‐DL‐alanine DEA, adsorption of DL‐β‐phenylalanine NCA onto the polymer chain takes place, though not so effectively as with other polypeptides, so the absence of chain effect was ascribed to a reduced flexibility of the polymer chain. With poly(N‐benzylglycine)DEA, the reactivity of terminal base group was found to be much lower than that of other polymer catalysts. However, the absence of the chain effect would be attributed to the rigidity of polymer chain of poly‐N‐benzylglycine DEA due to the bulkiness of the N‐benzyl group.