Different Routes to Ampholytic Polydehydroalanine: Orthogonal versus Simultaneous Deprotection.

Polydehydroalanine (PDha) is a polyampholyte featuring both a -NH and a -COOH in every repeat unit and with that presents a rather high charge density. The synthesis and polymerization of two monomers, benzyl 2-tert-butoxycarbonylaminoacrylate and methyl 2-benzyloxycarbonylaminoacrylate is herein reported, which feature different protective groups and, after polymerization, the resulting PtBABA and PBOMA can be transformed into PDha using polymer-analogous modification reactions. More important, the current choice of protective groups allows either simultaneous deprotection in one step in both cases, but also the orthogonal deprotection of either -NH or -COOH moiety for PtBABA, given that appropriate conditions are chosen. The polymers are prepared using free radical polymerization and all (intermediate) polymeric materials are investigated using a combination of NMR spectroscopy and size exclusion chromatography.