Rapid Synthesis of Functionalized High-Generation Polyester Dendrimers via Strain-Promoted Alkyne–Azide Cycloaddition

Preparation of structurally perfect high-generation dendrimer libraries with different peripheral groups is challenging as divergent synthesis introduces peripheral defects and convergent synthesis leads to low yields. Here, we prepare a third-generation polyester dendron based on the bisMPA monomer structure, having eight peripheral azide functionalities, as an “inner” dendron. We also prepare a series of low-generation “outer” dendrons (G2 and G3) with various peripheral groups, including aromatic, aliphatic, and polar structures, each having a single dibenzoaza­cyclooctyne (DIBAC) at the core. Efficient strain-promoted azide–alkyne cycloaddition (SPAAC) enables quantitative coupling between the outer and inner dendrons, producing high-generation (G5 and G6) dendrimers in a single coupling step. Characterization by NMR and mass spectrometry shows that the coupling products are structurally perfect. Using this strategy, we prepared a small dendrimer library that includes the first high-generation monodisperse peripherally PEGylated dendrimers as well as a structure bearing bulky protected amino acids at its periphery. This general strategy allows for rapid, efficient, and quantitative preparation of high-generation dendrimers with a variety of peripheral and core functional groups, starting from small, easily prepared fragments.