Chiral dendrimers with axial chirality

Abstract

The synthesis and optical activity of novel chiral dendrimers with axial chirality are reported. The dendrimers were constructed by coupling of the polyether dendritic bromides with (R)-(+)-1,1′-bi-2-naphthol (1). The uniform (2, 3, 4) and non-uniform double-O-alkylated (8, 9, 10) as well as mono-O-alkylated (5, 6, 7) products were thus obtained. These chiral molecules were characterized by 1H- and 13C-NMR, elemental analysis, optical rotation, adsorption spectra, and circular dichroism. It was found that the specific rotation decreases with the increase of the number of generation for each group of dendrimers (2–4, 5–7, and 8–10, respectively). In terms of the molar rotation, it was quite different; the molar rotation increased sharply for dendrimers, 2–4, but only slightly for dendrimers 5–7. The dihedral angle change of bi-naphthyl in the synthesized dendrimers was discussed based on the CD spectra. Chirality 10:661–666, 1998. © 1998 Wiley-Liss, Inc.