Synthesis and properties of optically active amino acid based polyacetylenes bearing eugenol and fluorene moieties

Abstract

Novel optically active amino acid based polyacetylenes bearing eugenol and fluorene moieties were synthesized, and their properties, including chiroptical ones, were analyzed. N-[1-(3,4-Dimethoxyphenyl)-2-propyloxycarbonyl]-L-alanine N′-propargylamide (1), N-[1-(3,4-dimethoxyphenyl)-2-propyloxycarbonyl]-L- alanine propargyl ester (2), N-(9-fluorenylmethoxycarbonyl)-L-alanine N′-propargylamide (3), and N-(9-fluorenylmethoxycarbonyl)-L-alanine propargyl ester (4) were polymerized with a rhodium-zwitterion catalyst in tetrahydrofuran to afford the corresponding polymers with moderate molecular weights ranging from 10,800 to 17,300 in good yields. Because of the large specific rotation and circular dichroism (CD) signal, it was concluded that the poly(N-propargylamide)s [poly(1) and poly(3)] took a helical structure with a predominantly one-handed screw sense. The solvent and temperature could tune the helical structure of poly(1). On the other hand, the poly(propargyl ester)s [poly(2) and poly(4)] exhibited only small specific rotations and CD signals. © 2005 Wiley Periodicals, Inc.