Synthesis of multivalent carbonate esters by divergent growth of branched carbamates

Multivalent 4-nitrophenyl (PNP)–carbonate esters were prepared from carbonate ester-containing core groups by a new divergent-growth process. The process doubles the number of PNP–carbonate esters with each round of growth, or branching, which occurs by reacting an N,N-dihydroxylalkyl amine with a PNP–carbonate ester. The resulting N,N-dihydroxyalkyl carbamate contains two hydroxyl groups for each original PNP–carbonate ester. The hydroxyl groups are converted in situ to PNP–carbonate esters, and the process can be repeated to provide successive generations of dendrimer-like branched structures of increased valence.