Chirality and dendrimers; the issue of chiral recognition at the nanoscopic level

Abstract

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 four constitutionally different, but chemically resembling, branches to an achiral core. A multi‐substituted pentaerythritol derivative is used as core and Fréchet's aromatic‐ether dendritic wedges of different generation are used as branches. The synthetic approach makes use of the consecutive attachment of the four branches by selective deprotection of the core. Both chiral dendrimers of different size have been synthesized from the same precursor. 1H‐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 have not been successful so far, giving rise to a discussion on the degree of chirality in these dendrimers of nanometer dimensions.

Convergent Dendrons and Dendrimers: from Synthesis to Applications

“…Meijer and co-workers have prepared an interesting set of molecules with chirality that originates from dendrons of different generation radiating from an otherwise achiral pentaerythritol core. − Unfortunately, attempts to resolve the racemic products were unsuccessful, and the chirotopic properties of the materials could not be studied. However, the same group later reported the successful preparation (Figure ) of the optically pure ( R ) and ( S ) enantiomers 177a and 177b , by Williamson coupling of Fréchet-type dendrons to a chiral glycerol derivative using a series of protection and deprotection steps …”

Chiral dendrimers—from architecturally interesting hyperbranched macromolecules to functional materials

“…The inability to resolve the enantiomeric forms of the polyether dendrimers using chiral HPLC analysis was justified by consideration of the different 'dimensions' of chirality between the stationary phase, whose chirality is expressed at a molecular level, and the macroscopic chirality of the hyperbranched macromolecules. 72 The Eindhoven-based group 73 has also prepared closely related chiral dendritic macromolecules (9a and 9b in Fig. 7) in the (R) and (S) pure forms employing the chiral glycerol derivative (S)solketal as the starting material.…”