Polymeric and dendrimeric pyridoxal enzyme mimics

Abstract

Pyridoxal was covalently attached to polyethylenimine polymers, but the resulting materials were found to degrade rapidly. In comparison, the dendrimeric pyridoxals, which possess only one pyridoxal unit at the core of every dendrimer molecule were found to be relatively stable compounds. A total of 12 poly(amidoamine) type dendrimers were synthesized. They range from G1 to G6 with either NMe 2 or NHAc termini. The NMe 2-terminated pyridoxal dendrimers racemize α-amino acids 50–100 times faster than does simple pyridoxal, while the NHAc-terminated pyridoxal dendrimers racemize α-amino acids only 3–5 times faster than does simple pyridoxal. Both the NMe 2- and NHAc-terminated pyridoxal dendrimers decarboxylate 2-amino-2-phenyl-propionic acid 1–3 times faster than simple pyridoxal. The interior polarity in the pyridoxal dendrimers is similar to that of 85:15 water–DMF solution. Furthermore, we successfully incorporated eight lauryl groups to the G5 pyridoxal dendrimer at known positions. The laurylated dendrimer exhibits lower racemization and decarboxylation rates than do the unlaurylated ones, in contrast to the positive rate effects of laurylation in polyethylenimine–pyridoxamines in our previous transamination studies.