Abstract
The present report describes our current efforts to determine the nature of the cis/trans isomerization observed for poly(l-proline). Previously, we examined the effect that a substituent in the 5-position of the pyrrolidine ring had on the preferred conformations of poly(l-proline). We concluded that a bulkier group was needed in order to see significant changes in the conformation of polyproline. Thus, the synthesis of optically active poly(cis- and trans-5-isopropylproline) is described. The synthesis of the monomers involves the formation of Δ′-2-isopropylpyrroline-5-carboxylic acid hydrochloride (III) which is prepared from the Michael adduct obtained from the reaction of 1-chloro-4-methyl-3-pentanone with diethylacetamidomalonate. Catalytic hydrogenation of III gives the hydrochloride salt of cis-5-isopropylproline. The trans isomer is obtained through a chemical separation method that depends on difference in reactivity between the cis and trans isomers to p-toluene sulfonyl chloride. The optical resolution of both isomers is carried out using fractional crystallization methods. Polymers of optically active cis- and trans-5-isopropylproline are obtained by ring-opening polymerization of the corresponding N-carboxyanhydrides. Low yields encountered in the polymerization of poly(cis-5-isopropylproline) can be attributed to instability of the N-carboxyanhydride. The possibility that ring conformation may be seriously altered by the presence of a large group in the 5-position is briefly considered.
Similar content being viewed by others
Article PDF
References
L. Mandelkern, “Poly-α-amino Acids,” G. D. Fasman, Ed., Marcel Dekker, Inc., New York, 1967, p. 675.
D. S. Clark, J. J. Dechter, and L. Mandelkern, Macromolecules, 12, 626 (1979).
D. S. Clark, J. J. Dechter, and L. Mandelkern, Macromolecules, 13, 533 (1980).
G. N. Ramachandran and A. K. Mitra, J. Mol. Biol., 107, 85 (1976).
S. S. Zimmerman and H. A. Scheraga, Macromolecules, 9, 408 (1976).
M. L. Tiffany and S. Krimm, Biopolymers, 6, 1767 (1968).
L. Mandelkern and W. L. Mattice, “Conformation of Biological Macromolecules and Polymers,” E. D. Bergmann and B. Pullman, Ed., Jerusalem Symp. Quantum Chem. Bio-Chem., 5, 121 (1973).
J. F. Brandts, M. Brennan, and L. N. Lin., Proc. Natl. Acad. Sci. U.S.A., 74, 4178 (1977).
F. X. Schmid and R. L. Baldwin, Proc. Natl. Acad. Sci. U.S.A., 75, 4764 (1978).
M. Levitt, J. Mol. Biol., 145, 251 (1981).
C. G. Overberger and Y. S. Jon, J. Polym. Sci., Polym. Chem. Ed., 15, 1413 (1977).
C. G. Overberger and K.-H. David, and J. A. Moore, Macromolecules, 5, 368 (1972).
C. G. Overberger and K.-H. David, Macromolecules, 5, 373 (1972).
C. G. Overberger and M. J. Han, J. Polym. Sci., Polym. Chem. Ed., 13, 2251 (1975).
C. G. Overberger and M. J. Han, J. Polym. Sci., Polym. Symp., 51, 155 (1975).
W. W.-Y. Yang, C. G. Overberger, and C. M. Venkatachalam, J. Polym. Sci., Polym. Chem. Ed., 21, 1643 (1983).
W. W.-Y. Yang, C. G. Overberger, and C. M. Venkatachalam, J. Polym. Sci., Polym. Chem. Ed., 21, 1741 (1983).
W. W.-Y. Yang, C. G. Overberger, and C. M. Venkatachalam, J. Polym. Sci., Polym. Chem. Ed., 21, 1751 (1983).
K.-D. Ahn and C. G. Overberger, J. Polym. Sci., Polym. Chem. Ed., 21, 1699 (1983).
F. Irreverre, A. B. Mauger, and B. Witkop, J. Am. Chem. Soc., 87, 4875 (1965).
W. J. Horsley and H. Sternlicht, J. Am. Chem. Soc., 90, 3738 (1968).
W. J. Horsley, H. Sternlicht, and J. S. Cohen, J. Am. Chem. Soc., 92, 680 (1970).
H. C. Beyerman, Rec. Trav. Chim., 78, 134 (1959).
R. E. Sievers (Ed), “Nuclear Magnetic Resonance Shift Reagents,” Academic Press, New York, 1973, p 87.
E. Jizuka and J. T. Yang, Biochemistry, 13, 1519 (1964).
Recently, it was brought to our attention that both Amberlite IR-45 and IR-45 are no longer commercially available. We are currently investigating the possibility of using other ion exchange resins that are specifically designed for the removal of strong acids.
A. I. Vogel, “A Textbook of Practical Organic Chemistry,” 3rd ed, J. Wiley and Sons, New York, 1962, p 368.
A. A. Randall, J. Chem. Soc., 374 (1962).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
McGrady, K., Overberger, C. Synthesis of 5-Isopropyl-Substituted Poly(l-proline)s: Optically Active cis- and trans-5-Isopropylproline and Poly(cis- and trans-5-isopropylproline). Polym J 19, 539–555 (1987). https://doi.org/10.1295/polymj.19.539
Issue Date:
DOI: https://doi.org/10.1295/polymj.19.539