Polymerization and conformational studies of poly(trans -3-ethyl- D and L -proline)

Poly(L - trans -3-ethylproline), L -PT3EP, and poly(D - trans -3-ethylproline), D -PT3EP, were prepared by ring opening polymerization of the corresponding N -carboxyanhydrides (NCA) using triethylamine as an initiator. Using circular dichroism spectroscopy, it was shown that the incorporation of an ethyl group at the 3 position of the pyrrolidine ring caused a noticeable change in the conformational behavior of the polymer in solution. The ethyl group limited to some extent rotation of the polymer chain around the C [bond] [bond]CO bond and prevented the mutarotation between the two forms found in poly- L -proline polymers.