Constitution, Configuration, and the Optical Activity of Chiral Dendrimers

Abstract

Three series of zeroth to second generation chiral dendrimers, 7−9, 10−12, and 13−15, were prepared by convergent methods using chiral, nonracemic AB2 monomers 1, 2, and 3, respectively. Chiroptical data revealed a significant change in molar rotation per subunit ([Φ]D/n) as dendrimer generation increased for dendrimers 7−9 and 10−12, but not for dendrimers 13−15, a possible indication of chiral conformational order in the former two series of dendrimers, but not in the last. However, the optical activities ([Φ]D) of low-molecular-weight model compounds 16 (+262) and 17 (+122), prepared to simulate different regions of the dendrimer structure, suggest that as generation size increases slight constitutional changes have a strong effect on the chiroptical properties of the dendrimer subunits. Using the [Φ]D values of these and other (18−23) low-molecular-weight model compounds, we calculated [Φ]D values for dendrimers 7−15 that agree within 14% of the observed values. Agreement between the optical activity ...