The chirality of dendrimer-based supramolecular complexes

Boc-protected l-phenylalanine has been connected to a spacer-armed ureido-acetic acid deriv., which can form multiple supramol. complexes with urea-adamantyl modified poly(propylene imine) dendrimers in chloroform. Complexes of this guest with several generations of urea-adamantyl dendrimers were prepd. The dendrimer-guest complexes were characterized in detail by 1H-NMR, 1H-1H-NOESY spectroscopy and mass spectrometry to prove their formation. Optical rotation expts. performed on different generations of dendrimer-guest complexes showed a const. pos. value. These observations indicate that, though guest mols. decrease the flexibility at the periphery of the dendrimer upon binding, the amino acid at the terminus of the guest mol. retains its high local conformational freedom. This is in agreement with values found for covalently modified spacer-armed dendrimers.