Chiral dendrimers derived from pentaerythritol

The synthesis and characterization of two chiral dendrimers, 1 and 2, in their racemic form is presented. The chirality is based on the construction of 4 constitutionally different, but chemically similar, branches to an achiral core. A multi-substituted pentaerythritol derivative is used as core and Frechet's aromatic-ether dendritic wedges of different generation are used as branches. The synthetic approach makes use of the fact that the 4 branches are attached consecutively by a selective deprotection of the core. Both chiral dendrimers of different size have been synthesized from the same precursor. H-1-NMR spectroscopy indicates an overall chiral shape for 1, while for both 1 and 2 stratified structures are observed. Several attempts to resolve both dendrimers into their individual enantiomers have not been successful so far, giving rise to a discussion on the degree of chirality of these dendrimers of nanometer dimensions.