Synthesis and characterization of chiral polyamides derived from glycine and (S)-5-amino-4-methoxypentanoic acid

Stereoregular, enantiomerically pure, chiral polyamides of the -AB- type, containing a natural (glycine) and a synthetic [(S)-5-amino-4-methoxypentanoic acid (AMP)] component have been prepared by the active ester polycondensation method. Thus, polyamide 7 was obtained by polycondensation of the conveniently activated H(2)NGly-AMPCO(2)R unit (6). In this reaction, 7 appeared accompanied by a considerable amount of cyclic (Gly-AMP), (8), which makes the isolation and purification of 7 difficult. The formation of cyclic byproducts could he avoided by preparing and polymerizing the oligoamide H(2)NGly-AMP-AMPCO(2)R (11), which has the terminal carboxyl group activated as the pentachlorophenyl ester. The resulting polyamide (12) was obtained in 85% yield and free of macrolactams, such as 8. The new polyamides 7 and 12 were characterized by elemental analysis and infrared and H-1- and C-13-nuclear magnetic resonance spectroscopies. Thermal studies revealed that 12 is crystalline and yields films with spherulitic texture by slow evaporation of formic acid solutions. (C) 1998 John Wiley & Sons, Inc.