Synthesis of multivalent carbonate esters by divergent growth of branched carbamates

Multivalent 4-nitrophenyl (PNP)-carbonate esters were prepared from carbona te ester-containing core groups by a new divergent-growth process. The proc ess doubles the number of PNP-carbonate esters with each round of growth, o r branching, which occurs by reacting an N,N-dihydroxylalkyl amine with a P NP-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 repe ated to provide successive generations of dendrimer-like branched structure s of increased valence. (C) 2001 Published by Elsevier Science Ltd.