DOUBLE EXPONENTIAL DENDRIMER GROWTH

An exponentially accelerated convergent growth scheme for the synthesi s of dendritic macromolecules is described and demonstrated. By this p rocess, the number of repeat units per dendrimer accumulates according to a double exponential function in terms of generation, n. The proce ss employs a single trifunctional monomer of the type A(p)(B-p)(2) hav ing orthogonally protected functional groups. The repetitive process i nvolves selective removal of the protecting groups on A(p) in one port ion, selective removal of the protecting groups on B-p in a second por tion, and subsequent coupling of the two monoprotected intermediates i n a proper stoichiometric ratio. The new monodendron maintains a singl e A(p) group at its focal point but contains x(2)B(p) peripheral group s where x is the number of peripheral groups in the preceding generati on. The double exponential growth scheme is demonstrated by the synthe sis of a third-generation (255-mer) phenylacetylene monodendron that i s characterized by ultraviolet matrix-assisted laser desorption/ioniza tion (MALDI) mass spectrometry (calculated molecular weight 39.972 kDa , observed m/z 39.969 kDa).