Synthesis of Well-Defined Bifunctional Newkome-Type Dendrimers

Four bifunctional Newkome-type 1 → 3 branched polyamide-based dendrimers with different spatial arrangements of azido and alkenyl termini were synthesized. The dendrimer synthesis started with three building blocks containing two different ester protecting groups that can be deprotected in an orthogonal fashion. This orthogonal deprotection strategy allowed for the synthesis of three bifunctional dendrimers in a convergent fashion and one dendrimer via a divergent synthetic route. These four dendrimers have different spatial arrangements of termini capable of undergoing further functionalization using 1,3-dipolar cycloaddition and thiol-ene type click chemistries. The precise placement of the functional moieties along the dendrimer surface allows for dendrimer functionalization with a known ratio of cargo and exact placement on the periphery.