Synthesis of chiral polyhydroxy polyamides having chains of defined regio and stereoregularity

1,6-Diaminohexane and a 2-(S)-hydroxypentanedioic acid 5,2-lactone derivative (3) were polycondensed to afford an aregic polyamide 4. A chiral monomer (5) having a a-fold axis of symmetry was chemoselectively constructed from 3, and upon polymerization with the diamine led to an AABB-type polyamide having a syndioregic orientation of the hydroxyl substituents. The analogous isoregic polyamide 11 was also prepared. The three polymers had the same basic structure, but they differ in their regio and stereoregularity. These polyamides, which displayed optical activity, were characterized by IR and H-1 and C-13 NMR, and their molecular weights were estimated by GPC, viscosimetry, and matrix-assited ultraviolet laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI-TOF MS). This technique was particularly convenient to confirm the repeat units and to detect the functional groups at both ends of the chains. In accordance with their growth processes polyamides 11 and 12 showed the typical UV-MALDI-TOF spectrum for homopolymerization, and polyamides 4 and 6 showed those corresponding to growing by copolymerization. Besides, in agreement with their stereoregularity, polyamides 6 and 11 showed better crystalline properties than those of 4.