Synthesis of uniform poly(aspartic acids)

Poly(aspartic acids) of different chain lengths (11, 14, 18, 24, 30, 52, 58, ≈ 115) were prepared, for the use in aminoglycoside-induced nephrotoxicity inhibition studies, some in their pure L - or D -configuration and in pure α-linkage form by the polymerization of α-amino acid N-carboxyanhydride (NCA) derivatives with a variety of dialkyl aspartate molecules as primary amine initiators. The primary amine chosen served as an internal reference in the ¹H NMR spectrum for the estimation of the degree of polymerization (chain length) in these molecules. Poly(aspartic acids) with varying amounts of D and L asymmetric centres and in pure α-linkage from were also prepared. Poly[(α-co-β)(L -co-D ) aspartic acid] was prepared by a simplified thermal polymerization procedure for biological studies and also to study the tacticity effects in its ¹³C NMR spectrum. A qualitative correlation was demonstrated between the retention times from gel-permeation chromatographic analysis and the ¹H NMR method used to estimate the polymer chain length.