Synthesis of regioisomeric, stereoregular AABB-type polyamides from chiral diamines and diacids derived from natural amino acids

Two regioisomeric and stereoregular AABB-type polyamides have been synthesized using l-glutamic acid 1 and l-alaninol 4 as sources of chirality. From 4, two derivatives of chiral diamines were prepared and regioselectively condensed with pentachlorophenyl 5-oxo-(S)-2-tetrahydrofurancarboxylate 3, derived from 1. Manipulation of functional groups and convenient deprotections led to the ammonium salts of N-[1′-amino-(S)-2′-propyl]- and N-[(S)-2′-amino-1′-propyl]-5-oxo-(S)-2-tetrahydrofurancarboxyamide 11 and 15, respectively, in which the building blocks derived from 1 and 4 are linked through an amido group. Compounds 11 and 15 are, in fact, α,ω-amino acids having amino and lactone groups, and hence activated for polycondensation. Thus, polymerization of 11 took place under regio- and stereo-control to afford stereoregular poly[N-(1′-amino-(S)-2′-propyl)-carboxyamido-(S)-2-hydroxypentan-5-oic acid] (16). Similar polycondensation of 15, under the optimized conditions employed for the synthesis of 16, gave the regioisomeric polyamide 17, which exhibited a molecular weight lower than that of 16. The thermal and spectroscopic properties of optically active AABB-polyamides 16 and 17 are described.

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N-(1′-Amino-(S)-2′-propyl)-5-oxo-(S)-2-tetrahydrofurancarboxyamide hydrochlorideC8H14N2O3·HClEe = 100%[α]D24=+40.0 (c 1.0, DMSO)Source of chirality:l-alanine and l-glutamic acid

N-[(S)-2′-N-(tert-Butoxycarbonyl)amino-1′-propyl]-5-oxo-(S)-2-tetrahydrofuran carboxyamideC13H22N2O5Ee = 100%[α]D24=-17.2 (c 1, CHCl3)Source of chirality:l-alanine and l-glutamic acid

N-[(S)-2′-Amino-1′-propyl]-5-oxo-(S)-2-tetrahydrofurancarboxyamide p-toluenesulfonateC8H14N2O3·2CH3C6H4SO3HEe = 100%[α]D24=+10.6 (c 0.6, DMSO)Source of chirality:l-alanine and l-glutamic acid

N-[(S)-2′-Amino-1′-propyl]-5-oxo-(S)-2-tetrahydrofurancarboxyamide trifluoroacetateC8H14N2O3·1.5F3CCO2HEe = 100%[α]D24=+5.8 (c 1, DMSO)Source of chirality:l-alanine and l-glutamic acid

Poly[N-(1′-amino-(S)-2′-propyl)-carboxyamido-(S)-2-hydroxypentan-5-oic acid]C8H14N2O3·0.5H2OEe = 100%[α]D24=-27.4 (c 1, DMSO)Source of chirality:l-alanine and l-glutamic acid

Poly[N-[(S)-2′-amino-1′-propyl]-carboxyamido-(S)-2-hydroxypentan-5-oic acid]C8H14N2O3·nH2OEe = 100%[α]D24=-15.0 (c 0.5, DMSO)Source of chirality: l-alanine and l-glutamic acid