Helical conformation of the copolymers of l-proline derivatives based propargylether and chiral N-propargylamide

The novel acetylene monomers, l-proline derivatives based propargylethers PR (PA, PC, and PL) were synthesized by alkylation of Boc-hydroxyproline with propargyl bromide and acylation of achiral amine. The homopolymers of the novel acetylene monomer exist in no regulated higher order structure in solvents because of the lack of hydrogen bond and the unique ring structure in the pendant. Consequently, the copolymerization of l-proline-derived chiral propargylether PR with the l-alanine-derived N-propargylamide (LA) was formed and the chiroptical properties of the formed copolymers were examined. We conclude that (1) N-H of the amide group at 2-position in proline play an important role in the formation of helical conformation of poly(LA88-co-PR12); (2) improving the amount of PC of poly(LA-co-PC) changes the conformation of the copolymer in CHCl3 and perturbs the leadership of LA; (3) the conformation of poly(LA75-co-PC25) remarkably changes with changing temperature and PC obtains the leadership in the competition on the conformation of poly(LA75-co-PC25) in CHCl3 with the improvement of temperature.